10. Suggested resources for more tips on language editing in the sciences

9. Measurements and their descriptions

English uses adjectives like high or low and greater or lesser as adjectives to express the volume, size, or quantity of a measurement. The following chart of descriptive words in scientific papers can help in finding the standard adjective to fit common types of measurements.

high or low abundance, absorption, accuracy, adiabaticity, background, brightness, contrast, degree, density, energy, extinction, fraction, frequency, latitude, level, luminosity, mass, metallicity, number, obliquity, percentage, precision, pressure, probability, proportion, quality, rate, redshift, resolution, shear, speed, temperature, value, velocity.
big/large or small amplitude, broadening, diffusivity, momentum, opacity, proper motions, radius, uncertainties
high/low or large/small dispersion, frequency, magnitude, number statistics
wide/broad or narrow range, spread, variety
steep or shallow gradient, slope
long or short burst, length, period, time, timescale
strong or weak acceleration, anisotropy, argument, asymmetry, constraint, contrast, current, dependence, effect, evidence, magnetic field, flow, gradient, instability, pulse, relevance, shear, turbulence, velocity field
tight or loose relationship, constraint, correlation
note: strong and weak can also be used in these instances

8. Common editing issues

Here is a list of the common errors that A&A language editors tend to see in papers.

8.1 Nouns

Data uses the plural form of the verb, however data set and data point take the singular


  • We extrapolated the data and found that they were incorrect.
  • We reported that our data set was insufficient and we needed to obtain further data points.

While statistics is plural in form, the verb form can be either plural, when referring to a collection of data, or singular, when referring to the discipline. However, a set of statistics always uses the singular form of the verb.


  • The statistics show that many of the observations were impacted by noise.
  • This set of statistics was undermined by the results of the latest study.
  • is concerned with compiling, organizing, analyzing, and interpreting data.

Dynamics uses the singular form of the verb.

Example: The dynamics of the system was described by a quantum master equation.

Galaxy cluster refers to a cluster of galaxies (the “ies” from “galaxies” is dropped in this case).

Example: This galaxy cluster contains hundreds of thousands of stars.

8.2 Verbs

Usage: to account for; to take into account
Examples: We account for this discrepancy in our calculations.
We take this discrepancy into account when checking our results.

Usage: to agree with; to be in agreement with
Examples: Our results agree with the findings published in the literature.
Our data are in agreement with the findings of a previous study.

Usage: to aim to; to be aimed at
Examples: In this study, we aim to show the consistency and stability of the Nuker models.
This study is aimed at demonstrating the significance of the inner density slope within the model.

Usage: to allow for; to allow something/someone to do something
Examples: This assumption allows for a precise calculation.
These innovative telescopes allow us to make more precise observations.

Usage: to correct for
Example: We used this method to correct for the skewed measurement in our calculations.

Distinguish; differentiate
Usage: to distinguish from; differentiate from
Example: We used the color red to distinguish our results from those of the previous study.

8.3 Pronouns and relative pronouns

et al.
This expression refers to a team with more than one author and uses the plural form of the verb. When making reference to authors, referees, or other individuals, confusion about pronouns can be avoided by using the neutral they form in references and acknowledgements.


  • El Mellah et al. (2019b) suggest that this mechanism is chiefly responsible for the formation of ultra-luminous X-ray sources (ULXs). We thank the referee for their comments.

That; which
These are relative pronouns that have a similar meaning but which are used differently in a sentence. A&A style leans towards the use of that when providing essential and defining information about a subject because it is a more direct expression of the relationship between the subject and the description.


  • An effective gating mechanism that hampers the accretion of the transferred material seems to be at work in these systems, which has a negative impact on X-ray luminosity.
  • The galaxy that contains approximately one trillion stars also has satellite galaxies. (i.e., there is more than one galaxy and the fact it has one trillion stars is the defining element.)
  • The galaxy, which contains approximately one trillion stars, also has satellite galaxies. (i.e., there is at least one galaxy and the additional information about the one trillion stars is nonessential.)

Note: There should not be a comma before that (unless it is preceded by another, separate clause in a complex sentence) but which can be used with or without a comma, depending on the structure and complexity of a sentence.

8.4 Expressions of size, number, and scope

Example: None of the parameters were met.

One of
Example: She is one of the best astronomers in the world.

Many; a number of
Examples: There have been many papers written on the subject. A number of researchers have studied this topic. There were a number of researchers taking part in the study.

Majority; minority (implies more or less than 50% of something)
The majority of researchers rely on this funding to carry out their work.

Fraction (implies a small portion)
Only a fraction of our results were in agreement with the hypothesis.

7. General hyphenation guide

Hyphens are what make the difference between a man-eating alligator and a man eating alligator.

Generally, the Chicago Manual of Style recommends that you should hyphenate compound phrases to avoid misdirecting the reader. When it doubt, they say, look it up in the dictionary. The goal of hyphens is to improve clarity on the relationships between words in a compound phrase. If there is a possibility the reader may be confused, it is best to use the hyphen and apply it consistently to a given phrase throughout the paper.

Examples of how hyphens can change the meaning of a phrase:

  • All inclusive classrooms are to be commended. (all classrooms that are inclusive)
  • All-inclusive classrooms are to be commended. (classrooms that are all-inclusive)
  • He submitted nine page reports that morning. (nine reports of one page)
  • He submitted nine-page reports that morning. (more than one report of nine pages)

When there is no possibility of ambiguity, there is no reason to use the hyphen unless it is standard usage, such as well-known, ill-humoured, long-term. Words that might be misread because the merged form already exists and has a distinct meaning should also gain a hyphen, such as re-form (form anew instead of reform) or re-pair (pair again instead of repair).

If the result is awkward, it is best to reword a sentence with too many hyphens.


  • The study covered a wide age-distance-metallicity-density parameter space.
  • The study covered a wide parameter space of ages, distances, metallicities, and densities.

Note: Two-word phrases with an adverb ending in ly are not hyphenated.

Examples: highly paid person, rapidly rotating planet.

Note: Compounds that use comparatives and superlatives with a participle (verb) have no hyphen.


  • fast-rotating galaxy; faster rotating galaxy; fastest rotating galaxy.
  • far-reaching findings; farther reaching findings; farthest reaching findings.

However, with compounds that use comparatives and superlatives with a noun, there is a hyphen:


  • high-mass star; higher-mass star (but: even higher mass star); highest-mass star.
  • high-resolution screen; higher-resolution screen; highest-resolution screen.
  • A high-mass star typically burns hydrogen faster than its lower-mass counterpart.

Hyphens in word-forming prefixes
Both UK and US conventions use merged and hyphenated word forms. The US spelling tends to merge common prefixes (e.g., multi, over, non) in compound nouns or adjectives, whereas the UK spelling is more likely to hyphenate.


  • We used a non relational database.
  • We used a nonrelational database (US convention)
  • We used a non-relational database (UK convention)

General note: The Chicago Manual of Style reports that with frequent use, both open and hyphenated compounds tend to become closed (as in the case of on-line to online; broad-band or broad band to broadband) and that is either reflected in the dictionary or should be expected to be reflected in an upcoming edition. This is why you may seem some discrepancy among spelling and hyphenation among various papers written by scientists from all over the world.

Here are some more points on when and how to use hyphens from the American Psychological Association: https://apastyle.apa.org/learn/faqs/when-use-hyphen

6. Verb tenses

You are likely to find yourself shifting between tenses in your paper depending on what aspect of your findings you are discussing. In general, A&A style uses the present tense to describe general facts, findings, truths, methods, and results from papers published within the last ten years. We use the past tense to describe the specific steps of the method used in your study or another study by a different author or group of authors. Here are some tips on when to use the past tense and when to use the present.

6.1 Present simple and past simple

Use the present simple for:

  • statements of fact and general truths
  • general findings from other authors, particularly recent ones (from the last ten years)
  • general methods used in the field (not the specific steps you used in your study)
  • general descriptions of your results and findings, including any discussions or conclusions
  • descriptions of tables and figures included in the paper

Time markers for the present include: now, usually, often, currently, at present, in this paper, etc.
The context will also indicate the tense that is appropriate for each part of your paper. The introduction, for example, tends to offer the reader a general background for the current study so it is typically written in the present tense.


  • In the usual reduction procedure, the data are measured and flux-calibrated.
  • Herschel images allow us to detect new YSOs.
  • In this paper, we find that the emission could be fully non-thermal at 5 GHz.

Use the past simple for:

  • specific steps you took as part of your method for your study (not general methods)
  • specific steps taken as part of a method by other authors and scientists (not general methods)
  • specific methods taken by other authors as well as their findings from studies in the distant past (e.g., more than ten years ago)

The past tense is frequently used in the body of the paper where you describe the specific actions you took in your study to achieve your final results, such as: we took, we carried out, we measured, we calibrated, we used, we observed, we calculated, we deduced, we assumed, we concluded.


  • In our study, we measured and flux-calibrated the data.
  • We detected 16 YSOs based on the Herschel images.
  • Using this method, we found that the emission was fully non-thermal at 5 GHz.

When describing your findings in the present tense, make sure that you also use the present for recent or current (within the last ten years) findings from other authors. Using the past tense when referring to the work of other authors could suggest that their findings are incorrect or out of date. Their specific methods, however, should remain in the past tense.

6.2 Present perfect and past perfect

These tenses are used to describe actions that occur over an extended period of time or at an unspecified point in time.They are generally not particularly useful in scientific writing.


  • Astronomers have used many different methods to study the Milky Way.
  • The authors had already published their paper by the time we finished ours.

There is also the present perfect continuous tense, which is used to describe an action that began in the past, continues in the present, and may continue into the future. Again, this tense is rarely necessary when writing a scientific paper.


  • The researchers’ results have been useful in providing a background for our own study.

Note: This tense can be used with phrases that serve as indicators of time, such as “in the past few years, in recent years, over the past few years” to extend the action through a period of time.


  • In recent years, several Seifert 2 galaxies have been discovered.

6.3 Present continuous and past continuous

These tenses are not recommended as there is seldom any need for the present or past continuous unless you are describing an ongoing action in the context of a simple action.


  • We conducted our study as night was falling.
  • It was proving difficult to calibrate the instrument due to environmental effects.

6.4 Future

In certain instances, you may use the future tense to describe upcoming studies or new equipment.


  • Crab pulsar rotation periods will be further examined in a forthcoming paper.
  • The JWST will provide greatly improved resolution and sensitivity.

Once in a while, you might find yourself needing to alternate between tenses when discussing things that happened at various points in time.


  • The Hubble deep field consists of 300 images that were taken in 1995. Such a large store of data had never been available before then.

5. Punctuation and style concerns regarding equations, figures, tables, and footnotes

Punctuate all equations in the body of the text with a comma or period where necessary according to their function in the sentence. If the equation ends a sentence, then it should be followed by a period (full stop). Please include a numbered reference with each equation and use that reference when discussing the equation in the body of the paper.

Figure and table legends
The first sentence of a figure caption or legend should be a descriptive title in telegraphic style, which omits the articles (the, a, an). The description that follows should concisely label and explain figures and parts of figures without going into too much detail. Additional details can be provided in the main text without duplicating the information provided in the captions.

Please make any footnotes as brief and succinct as possible.

4. UK versus US spelling and grammar

Depending on whether you are using American (US) or British (UK) style in your paper, please apply the given spelling and grammar conventions throughout. We provide some of the most common differences between these conventions below. We recommend setting your spellcheck tool to the convention you are using. Also, the most dependable dictionary for referencing US spelling is Merriam-Webster, while for UK spelling, it is the Cambridge Dictionary.

4.1 Spelling

UK conventions US conventions
• Nouns ending in
behaviour, neighbour, favour, colour, harbour, vapour behavior, neighbor, favor, color, harbor, vapor
Note: Contour is always spelled with an “our” ending for both US and UK styles.
• Nouns ending in
centre, metre, fibre, calibre center, meter, fiber, caliber
Note 1: Past participles also take the re/er ending: centred (UK) and centered (US).
Note 2: Parameter and diameter have the same spelling for both conventions.
• Nouns ending in
catalogue, analogue, isotopologue catalog, analog, isotopolog
• Nouns ending in
analyse, summarise, organise, ionise, normalise, minimise, practise analyze, summarize, organize, ionize, normalize, minimize, practice
Note 1: The related noun endings in -ization/-isation also follow the convention: organisation, ionisation (UK) and organization, ionization (US)..
Note 2: Authors can opt to use the “z” spelling in UK conventions (excluding “analyse”) as long as the use is consistent throughout a paper.
More differences in noun usage artefact, ageing, grey, speciality, sulphur, aluminium, disc (disk is a variant) artifact, aging, gray, specialty, sulfur, aluminum, disk
• Verbs ending in
model-modelling-modelled; label-labelling-labelled; cancel-cancelling-cancelled model-modeling-modeled; label-labeling-labeled; cancel-canceling-canceled
• Verbs ending in
fulfil; fulfilling; fulfilled; fulfilment fulfill; fulfilling; fulfilled; fulfillment
• Verbs ending in
focus; focussing; focussed (focusing and focused are variants) focus; focusing; focused
Other examples of differences in verb usage to inquire, to orientate (orient is a variant) to enquire, to orient
• Adverb towards, outwards, forwards toward, outward, forward
Note: In UK convention, when words ending in -wards are used in the adjective form, -ward is used (e.g., the forward movement).

4.2 More examples of differences between UK and US conventions

4.2.1 Formatting

Quotation marks: UK convention calls for the use of single quotation marks when formatting speech, titles, or when endowing a phrase with special meaning. US convention calls for double quotation marks in these instances. However, when quotation marks are used to show special meaning, they are only needed upon first appearance.

Note 1: If the special meaning is otherwise clear, or indicated by “so called” or similar, quotation marks or single quotation marks are not needed.

Note 2: When the end of a quote is just before a period or comma, in UK style the period or comma is outside of the closing quotation mark. In US style, the period or comma is placed inside of the quotation marks.


  • UK: Such alternative trajectories allow orbits that are along previously inaccessible field lines to 'escape'.
  • US: Such alternative trajectories allow orbits that are along previously inaccessible field lines to “escape.”
  • US/UK: According to Bert et al., this is a so-called rare phenomenon.

4.2.2 Hyphenation

UK convention calls for the hyphenation of certain prefixes that are merged in US English. Common examples are given below. See more on hyphenation further on in this guide.


  • UK: non-zero, north-east, multi-component, multi-wavelength
  • US: nonzero, northeast, multicomponent, multiwavelength

3. General structure

Published papers follow the same basic structure, with some small variations depending on the author’s own style: title, abstract, introduction, methods, discussion of the observations, results, and, finally, the conclusion.

3.1 Title

The title should be as brief and succinct as possible. Abbreviations should be avoided unless including the full name of the object, measurement, or instrument would make the title very long (i.e., more than three lines). Only the first word should be capitalized unless there is a proper noun, copyrighted name, or a specific instrument that requires capitalization. If you are using a subtitle, it can be separated from the main title by using a period, colon, or simply by skipping to the next line. Again, only the first letter of the subtitle should be capitalized, excluding the abovementioned exceptions. The discursive phrase “on the” should be avoided as it makes the title too wordy and often redundant. Additionally, it evokes Charles Darwin’s work “On the Origin of Species,” and it thus carries implied expectations along with it. Furthermore, puns or references to popular culture should be avoided in scientific articles, and titles in particular, especially since the meaning might be lost on some readers. Lastly, the use of questions in titles is strongly discouraged.

Note: Longer titles should be formulated using the corresponding latex command. If there are two parts to the title, the second part will be displayed as a subtitle and formatted at the production stage. For a paper that is part of a series, the generic series title will serve as the main title and the subject title will be numbered and displayed as the subtitle during production.

3.2 Abstract

When writing your abstract, it is recommended that you follow the traditional abstract layout of Context, Aims, Methods, Results, and Conclusions even if you choose not to use the headings in your text. Citations and references are not allowed in the abstract except under special circumstances; however, they must be included in the body of the main text. The abstract should be written in complete sentences.


  • Aims. In this study, we investigate stars.
  • In this study, we aim to investigate stars.

3.3 Body of the paper

The abstract should be followed by an introduction, which introduces the general context of the study. The rest of the paper should be split up into individual sections, each with its own theme and title. Sections can be further divided into subsections and sub-subsections if necessary. Every section, subsection, and subsubsection of the paper should be indicated with a header and numbered consecutively. Only the first word of a heading should be capitalized - unless it is a proper noun.

Note: Subsections and sub-subsections are not permitted in the introduction.


  • 1. Introduction
  • 2. LBGs
  • 2.1 Properties of LGBs with detected emission lines
  • 2.2 Properties of LGBs with a 3D radiative transfer

Each paragraph of every section should have its own focus that is introduced in the first sentence. This first sentence should provide a smooth transition or otherwise clear connection to the preceding paragraph and the entire section. The transition helps the reader follow the discussion. Logical connectors (thus, hence, so that) can aid in providing clarity but they should not be overused. Furthermore, single-sentence paragraphs are not allowed.


  • Twenty-five years ago, we published our first study of exo-planets. We recently carried out our latest observations based on the aforementioned study, which proved helpful in establishing constraints on our findings.

When making transitions, please be sure that it is clear what the pronoun and reference word you are using refer to (latter, aforementioned, that study, those authors, that finding). If there is any ambiguity, repeat the noun or phrase to which you are referring.


  • Smith et al. found that their measurement was not a good fit for the data, whereas Bart et al. reported that their findings were more precise than they had anticipated. This was an unexpected result for the entire scope of the project.

Possible solutions for clarifying whose findings these were and what was unexpected:

  • Smith et al. found that their measurement was not a good fit for the data, whereas Bart et al. reported that their own findings were more precise than they had anticipated. This discrepancy between measurements was an unexpected result for the entire scope of the project.
  • Smith et al. found that their measurement was not a good fit for the data, whereas Bart et al. reported that the findings of Smith et al. had actually been more precise than they had anticipated. This discovery was an unexpected result for the entire scope of the project.


  • In this paper, we present fluxes in the CI lines of neutral carbon at the centres of some 76 galaxies with far-infrared luminosities ranging from X to Y, as obtained with the Herschel Space Observatory and ground-based facilities, along with the line fluxes of the J=7-6 transition.

Possible solutions to clarify the role of the line fluxes in the sentence:

  • In this paper, we present fluxes in the CI lines of neutral carbon at the centres of some 76 galaxies with far-infrared luminosities ranging from X to Y, as obtained using the Herschel Space Observatory and ground-based facilities, along with the line fluxes of the J=7-6 transition.
  • In this paper, we present fluxes in the CI lines of neutral carbon at the centres of some 76 galaxies with far-infrared luminosities ranging from X to Y, as obtained with the Herschel Space Observatory and ground-based facilities. We also present the line fluxes of the J=7-6 transition.

Base your sentence structure on English declarative sentences, which are made up of a subject, predicate (central verb phrase), and object of the action. Subjects and verbs should be kept as close together as possible in a sentence to avoid confusion or ambiguity. Any ambiguity in phrasing will be flagged by the LE and rephrased directly or highlighted with a note asking the author to rephrase the sentence to clarify their meaning.

Note: While it is not grammatically incorrect to start a sentence with a dependent clause in English, it should only be used sparingly (e.g., when it improves readability).


  • The authors, after revising the English, submitted their article.
  • After revising the English, the authors submitted their article.
  • Especially appealing is the study of its stellar winds.
  • The study of its stellar winds is especially appealing.
  • To understand the observed diversity of these systems, the ultitude of physical mechanisms affecting low mass galaxy evolution, data on the ages, chemical abundances, spatial distribution, and kinematics of the stellar component of LG dwarf galaxies are needed.
  • The multitude of physical mechanisms affecting low mass galaxy evolution, data on the ages, chemical abundances, spacial distribution, and kinematics of the stellar component of LG dwarf galaxies are needed to understand the observed diversity of these systems.

Authors should also avoid separating a transitive verb from its direct object. While some adverbs go before the verb (often, rarely, clearly), an adverb generally follows either the object of the verb (transitive verb) or the verb when it is intransitive.


  • The star’s image shows clearly the alignment.
  • The star’s image clearly shows the alignment. (transitive verb)
  • The star’s image shows the alignment clearly. (transitive verb)
  • The number of small dwarfs increased exponentially. (intransitive verb)
  • The small dwarf increased in size exponentially. (transitive verb)

The subtle difference in meaning between the first two solutions above is based on emphasis. In the first example, there is emphasis on it being clear that the image shows the alignment (1) and in the second, the emphasis is on the fact that the alignment is shown clearly in the image (2). Another way to say this would be: The star’s image obviously shows the alignment (1) and The alignment is shown clearly in the star’s image (2).

Furthermore, certain prepositional phrases and idioms cannot be separated, such as: to take (something) into consideration or to take (something) into account.


  • We take into account the results of the study.
  • We take the results of the study into account.
  • We take the results of the study, which was published last year, into consideration.
  • We took the results of the study that was published last year into consideration.

A common error in usage is related to the verb: allow. The correct prepositions that should be used with allow are: to allow for; to allow someone to do something; and to allow something to be done.


  • The programme allows to analyse the data.
  • The programme allows for an analysis of the data.
  • The programme allows us to analyse the data.
  • The programme allows for the data to be analysed.

The synonyms enable and permit can also be used to replace allow when the word is overused.


  • The programme permits the analysis of the data.
  • The programme enabled us to analyze the data.

3.4 Acknowledgements

In this part of your paper, you have the opportunity to thank any referees or fellow researchers who helped in editing the paper, along with acknowledging any institutions that provided you or your team with academic or financial support.

Note: The language editors no longer correct the acknowledgements as they are not considered to be part of the scientific portion of papers. Please make sure you have corrected any errors or typos.

2. Main guidelines for A&A style

Consistency in punctuation, capitalization, spelling, hyphenation, and abbreviation is essential in maintaining the highest standard possible in any journal. The following sections explain the general rules of the A&A house style.

2.1 Acronyms and abbreviations

All acronyms and abbreviations should be spelled out upon first appearance in the body of the text and be followed by the acronym in parentheses. Once a term and its acronym have been introduced, you should use the acronym thereafter.


  • The High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph was mounted at the ESO 3.6m telescope in La Silla in 2003.

Note 1: A sentence should not begin with an acronym or abbreviation. Adding an article before the name can sometimes work to fix this issue; otherwise, please write out the name in full.

Note 2: The abbreviations e.g. and i.e. are acceptable when used in parentheses or figure and table legends; however, they should always be expanded when they are part of the main text. The abbreviation “e.g.” in the body of the text can be replaced with “for example,” “for instance,” or “such as,” whereas in the main body of the text, “i.e.” should be replaced by “that is” or a similar phrase. When using e.g. and i.e. in parentheses, please make note that in UK convention, there is no comma (e.g. and i.e.) while in US style, there is a comma (e.g., and i.e.,) when abbreviated.

Note 3: When giving location indicators throughout the paper, Sect., Fig., Eq., and Col. should always be abbreviated and capitalized when referring to a specific item, except when they are at the beginning of a sentence in which case they should be written out (Section, Figure, Equation, and Column).

Examples: Sect. 2, Sects. 2 and 3; Fig. 1, Figs. 1-4; Eq. (1), Eqs. (1), (2); Col. 1, Cols. 1-3.

Note 4: Table is never abbreviated, although it is capitalized when followed by its designated number. When any of these words are not followed by a specific item number, they are not capitalized or abbreviated.


  • This result can be found in the next section, where Eqs. (5) and (6) are discussed.

2.2 Capitalization

When it comes to capitalization, only proper nouns (Poisson, Solar Orbiter) and terms derived from proper nouns (Gaussian) are capitalized; this also applies to cardinal directions (north, south, east, west), which are in lowercase unless forming part of a proper noun (Chandra Deep Field South).

When giving the full name of a measurement, method, or other scientific terms, do not use capitals unless it comes from a proper noun (e.g., Poisson; Poissonian), the acronym has been formed from a combination of uppercase and lowercase letters, or the acronym is formed from other than the first letters.

Note: Earth, Moon, Milky Way, Solar System, and Galaxy are always capitalized but only when referring to Earth’s own Galaxy. Objects outside of our Galaxy should be written in lowercase.

Examples: star formation (SF), Atlantic Ocean (AO), the Galactic center (GC, when referring to our Galaxy), galactic center (GC, when referring to another galaxy), LOw Frequency ARray (LOFAR)

2.3 Commas and listing items effectively

Use the serial comma (also known as the Oxford comma) between three or more items that are listed consecutively. If a conjunction is used (and, or), the third comma should come before it. The word respectively can be used to clarify relationships between multiple sets of data. A semicolon can be used to further distinguish several consecutive sets of items or two independent ideas that are part of a complex sentence.

General notes on commas:

  • Commas should be used after introductory sentences of three or more words.
  • Commas should be used when splitting up or moving around the individual parts of a sentence (clauses) to improve clarity, especially in the case of complex phrases or sentence structures.
  • Commas are not necessary between two parallel items in a sentence.


  • In this paper, the estimation of rotation, glide, and quadrupole parameters are presented in Figs. 10, 11, and 12, respectively. We set the bin size at 20 for ICRF1 and published our results in a previous paper.

2.4 Date format

The date format in a paper must be consistent. To avoid ambiguity between UK and US styles of dates, we ask for the month to be spelled out and cardinal endings left out.

Examples: 4 January 2004; 4 Jan 2004; January 4, 2004; Jan 4, 2004; 2004 January 4; 2004 Jan 4

2.5 Headings and titles

For titles and headings, only the first word should be capitalized unless it is a proper noun, copyrighted name, or a specific instrument. When a colon appears in the title, the second part of the title is treated as a subtitle and the first word should also be capitalized. Abbreviations in the titles or headings should be avoided unless it renders the title too long (i.e., more than three lines).

Note: A colon should only be used when joining together two related but independent ideas. For the text appearing after a colon, the first word is not capitalized unless it is a full sentence, a proper noun, or part of a title or section heading.

Examples of titles and headings:

  • Radio afterglows of binary neutron star mergers: A population study
  • NGC 346 massive star census. Nitrogen abundances for core burning B-type stars
  • 5. Discussion and conclusions
  • 5.1 Twisted quasar light curves

2.6 Measurements

Standard units of measurement (cm, au, kg, s, h) do not need to be introduced unless they are mentioned individually, without any specific value.


  • We measured the distance in kilometers. Our result is 13 678 km.

Note: The tilde symbol (~) should only be used before measurements (~ 5 au) but not before text. Its textual equivalent is “approximately,” “on the order of” (US), or “of the order of” (UK).

2.7 Numbers

Write out numbers and ordinal numbers below 11 when they are not used as a measurement.


  • This was the second time we attempted to carry out observations at 5 GHz using the VLBA over the course of 12 years.

2.8 Parenthesis

Use parentheses to provide additional information, such as acronyms, brief elaborations, and, of course, references. Please avoid lengthy or numerous parenthetical phrases. If the text in parentheses can stand alone as a sentence, the parentheses are probably not necessary. Avoid parenthesis within parentheses, except when it is part of a formula. This includes the year in a reference that is placed in parenthesis, where we also prefer no comma between the name and year but do expect the period after “et al.”: (Johnson et al. 1999). When the name is in the text, only the year is in parenthesis. Also avoid placing two sets of parentheses together.


  • The ALLWISE catalog (Mainzer et al. 2011) was compiled after combining the data obtained during the cryogenic and post-cryogenic survey (NEOWISE) phases. These differences were noted by Tisserand (2012) and also mentioned earlier on in this paper (see Sect. 4).

2.9 Things to avoid

  • Avoid beginning a sentence with a number, a formula, or a symbol (in addition to an abbreviation or acronym, as mentioned above). To avoid this, you can either rephrase the sentence, add an article, or (in the case of a number or acronym) spell out the number/acronym.
    • Example:
      Ten years ago, our team of researchers began studying this phenomenon.
  • Avoid the use of bullets or lists in the body of the text. Bullet lists may be permitted in the conclusion as long as they are properly introduced with at least two sentences and there are a few concluding sentences after the last point of the list.
  • Avoid the contraction of verbs. Please write out verbs in full without any contraction. Correct usage is: do not, cannot, will not, it is, it is not, etc.
  • Avoid long and numerous footnotes where possible. For lengthy descriptions, please include as much as possible in the main body of the text.
  • Avoid italics for indicating emphasis. If you wish to place emphasis on a word, quotation marks are recommended - single for papers written in UK style (‘) and double for papers in US style (“). Quotation marks should only be used for emphasis the first time you use the word or phrase.
  • Avoid using informal language because it often creates ambiguity. For example, when making comparisons or giving examples, the word like should be replaced by such as, for example, or for instance.
  • Avoid using lengthy quotes from other papers. When possible, it is best to summarize the point you wish to make and provide the appropriate reference.
  • To avoid potential confusion, seasons (e.g., summer, fall/autumn, winter, spring) should be replaced with months as they are different in the Northern and Southern Hemispheres.
  • Avoid using slashes in the body of the text because these should be reserved for equations, ratios, and specific pairings of instruments. In place of slashes, we recommend using and, or, or a hyphen, as appropriate.

Note: A&A uses the abbreviation S/N for signal-to-noise ratio to avoid confusion with supernova remnant (SNR). There is no need to write out the word “ratio” after S/N as this is already indicated by the slash.

The A&A language guide for authors and language editors (2021 version)

The aim of this guide is to help you meet A&A standards when you are preparing your paper and to understand the linguistic and grammatical changes that language editors make to your paper.

This guide is not an extensive compendium of English grammar and style. It is meant to help our authors adapt to the house style of the journal and avoid common language errors. A general rule for this language guide is that consistency is key. It should be noted that language editors are not concerned with the overall structure of a paper as their role is solely to address linguistic ambiguities and errors.

There will always be variations in the English found in the journal as a whole, such as differences in spelling and sentence structure between British (UK) English and American (US) English, which we also cover in this guide. The following sections present the most important elements of A&A style and tips on how to ensure that your paper follows our guidelines.

1.1 Clarity and concision

In English, as in science, it is best to use precise phrasing for an idea. Please avoid paragraphs and sentences that are either too long or too short. Wordy constructions can often cloud the author’s intended meaning, and poetic language as well as cultural references should not be used.

1.2 Voice

We recommend authors mainly use the active voice and declarative structure (e.g., “We study”) in describing their methods and findings. While scientific writing in general may tend to use the passive voice in many cases, this often leads to wordy sentence structures. Please try to keep the subject, predicate (verb phrase), and object of each sentence in a logical sequence. This can help avoid ambiguity about which verb refers to which subject in a compound sentence.


  • That such observations can lead to accurate results is demonstrated by our analysis.
  • Our analysis demonstrates that such observations lead to accurate results.

Note: A&A avoids addressing the reader directly. For example, questions should not appear in papers and “note that” can either be deleted completely or replaced with “we note that” .


  • Note that the authors, after making substantial corrections, submitted the article.
  • We note that the authors submitted the article after making substantial corrections.

Guide to the English Editing at Astronomy & Astrophysics

J. Adams and M. Usdin

Observatoire de Paris, 61, Av. de l'Observatoire, 75014 Paris, France

This article contains the guide to the English editing at A&A.

1 Aims of this guide

The following language handbook can be used in different ways, which includes finding explanations behind some of the suggested changes. It was written based on the kinds of changes we recommend most often in A&A papers, so it does not pretend to be a full English language guide. The most useful time to use this A&A handbook is while working through the changes we have suggested in your accepted article, whenever you are not able to understand why a change was suggested. It not only contains details, but also tries to give a sense of the spirit behind certain types of changes we ask for, from some simple conventions about details of spelling or punctuation, through causes of ambiguity, to changes for the sake of rhetorical effectiveness. At times, for instance, some of these paragraphs will have been inserted into the yellow note boxes in your corrected version, when it occurs often in a paper. A second use might also be to take a look at it before submitting a paper so as to anticipate some of the changes we will suggest anyway, or alternatively as a `style guide' to supplement any you might be using at present.

2 Consistency of style: UK/US spelling conventions

A basic principle of our editing is to ask for consistency within an article, whether in the punctuation, capitalization, spelling, or abbreviations. One example is found in words that have more than one proper spelling or form: disc/disk, online/on-line/on line. A good dictionary will tell you both versions of any word, and some tell you which is more common. This dictionary will also let you know which spellings are American and which are British, when there are differences. There is only a small difference between the two conventions, but you need to use the same one throughout a paper. Use the following guidelines when asked to revise the spelling for this reason, and of course your text processor (including LATEX) can track this for you.

-OUR endings:
Behaviour, neighbour,
favour, colour, harbour, vapour
-OR endings (pronounced /or/): Behavior, neighbor,
favor, color, harbor, vapor
(NB, but "contour", pronounced /oor/)
-RE ending:
centre, metre
-ER ending:
center, meter
-SE ending on some verbs (less often for scientific terms)
analyse, summarise, organise
to practise (noun = practice)
Usually -ZE ending for the same verbs
analyze, summarize, organize

Doubled consonants on verb endings tend to be British, but are not strictly so:
Modelled, labelled, targetting
US English tends to the single consonant for endings if the pronunciation does not change.
Modeled, labeled, targeting
Expressions and others:
of the order of, in the order of

Brackets & square brackets
Further (or farther if distance)
Ageing, speciality
Catalogue, analogue, haloes, orientate
Fulfil, sulphur
Expressions and others:
on the order of (better: use the
standard synonyms: roughly, approximately, about)
Parentheses and brackets
Stricter on the difference
Aging, specialty
Catalog, analog, halos, orient
Fulfill, sulfur

3 Punctuation, abbreviation, and capitalization

As for all rules, some of the following are conventions chosen for stylistic consistency within the journal, which may be different from other journals. Most, however, are aiming to make the text clearer for readers, who are probably in a hurry, so anything that causes them to stop in order to understand or puzzle through a sentence may also make them stop reading altogether and go on to something else, which is neither the goal of the Journal nor the aim of any author.

How to write dates

In the text of your article, you may use either date formats common to regular prose (Day Month Year or Month Day Year) or the IAU recommended format (Year Month Day), as long as you remain consistent. Please use letters for the month, rather than using its figure, to avoid ambiguity.

When the date is an integral part of the events name, the use of the IAU format is recommended but not mandatory (for example, "the 2003 January 17 CME event"). Dates included in tables should be in IAU abridged format (for example, 2003 Jul 4).

Otherwise, you are free to choose from the following formats:
3 December 2005 / 3 Dec. 2005 /
Dec. 3, 2005 / December 3, 2005 /
2005 December 3 / 2005 Dec 3.

3.1 Punctuation

The serial COMMA in lists

In most technical and scientific writing, a comma precedes the `and' before the final item in a list of 3 or more[*]). In some cases, we may suggest a comma where it is inappropriate, but that probably shows that the list is ambiguously formulated, so it needs to clearly indicate which items are in the main list and which words modify those items.

The simple form is: X, Y, and Z. When any one of these is a compound, then the comma becomes essential: W, X and Y and Z. Should it be W, X and Y, and Z, where X and Y work as one element in the list? Or is it either an incorrectly punctuated list of 4 items (W, X, Y, and Z) or else only the last 2 work as a single unit: W, X, and Y and Z?

LISTS after colons

A colon is an appropriate way to introduce a long or a complicated list, and most authors do this correctly. No colon should follow the first one in a sentence and the sentence must end at the end of thatlist. To separate the items in the list, use commas when the items are simple and semi-colons for those that are complex, i.e., one or more of the elements require a comma due to a list or dependent clauses. Also it is expected that you keep each item parallel to the others (same part of speech or similar syntax, which is called "Parallelism" in language guides).

A simple example is
...as follows: the Earth, the Solar System, and the Galaxy

The complex formulations look more like:
...as follows: the Earth, but not the Moon; the Solar System and all its planets; and finally the Galaxy, which is part of the Universe.

Like the serial comma above, the combination of comma and semi-colon makes it clear which elements go in which part of the list. One place where colons are not needed is when introducing an equation that is separated in the layout but continues the syntax of the sentence, e.g., after a verb or a preposition, where no punctuation is needed. In fact, it would be incorrect in a normal sentence layout, so too here.

COLONS (or semi-colons) between 2 full sentences

That they are connected in the original shows that the author finds a relationship. In such a ase it is preferred that you use the logical connector that the ambiguous punctuation replaces with a comma; most often, this word is a causal connector, such as "because", "since", etc. It is possible to use these sentence connectors once in a while when the relationship is obvious to all, but make sure that there are not too many in each paragraph, which indicates a need to replace them with the logical connectors to help the reader follow your thought. Obviously connecting two sentences by only a comma (no logical connector) poses the same problem and is technically incorrect in English; but to be honest, there are very few authors who submit papers to A&A with this style error[*].

The preferred uses of the semi-colon between 2 sentences are either
(i) when one of the sentences, at least, is complex and contains one or more
commas or
(ii) a connector that requires a comma after it (however, moreover, hence) is used. The colon tends to be used mostly for introducing an example or a list.

COMMAS between two full sentences with a connector

The lack of a comma between two full sentences can be confusing at times, and it is needed for longer compound sentences, unless a semi-colon is more appropriate. Please consider that this is usually recommended in technical writing guides, except in very short sentences where there is no ambiguity as to their relationship.

COMMAS after introductory clauses

A comma is usually needed after a subordinate introductory phrase and the main clause, especially as it is often difficult to tell where the main clause begins, even for specialists. When this occurs with figures, it requires a lot of attention by the reader (In the interval 10 K < Tex < 30 K, F(Tex) is ...), but is often nearly impossible when following a long string of nouns used as modifiers, such that the final true noun and the first noun of the main clause become nearly undetectable.

Example: As previously emerging radiation spectra are calculated for a radius of the scattering cloud equal to the Bondi radius. Does the author mean As previously, emerging spectra are calculated or As for previously emerging radiation, spectra are calculated; or even, is this a fragment that introduces the next sentence?

If a specialist in this precise field might have to hesitate to decide between the two (or more) choices, one not a specialist will have to look much harder, will not understand, or will give up. A comma solves the problem for all cases and keeps your reader reading and following.

More often, authors invert the normal order of the English sentence, which is acceptable if not used constantly. There should be a reason for it, say for transition or rhetorical emphasis, rather than simply to vary the syntax.


"That" (not in phrases such as "enough ...that ...") is never preceded by a comma, because it introduces a restrictive clause. If tempted to use a comma there, then check that "which" is not more appropriate (=non-restrictive). That "that" is already used for so many functions makes it all the more necessary to keep to the conventions. Even though standard English allows which' to be used for the restrictive dependent clause, scientific articles prefer to keep the difference to the nonrestrictive even clearer by using only "that" without comma or "which" with a comma when nonrestrictive. Ex.: "Both metallicity components appear to have a common origin, which is different from that of the dark-matter halo." VS "Both metallicity components appear to have a common origin that is different from that of the dark-matter halo."

HYPHENS for two-word compounds when used together as an adjective

The rule is that the hyphen is used to connect the two words, e.g., adjective and its noun, when the second is used to modify another noun: "a region where stars are forming" becomes "a star-forming region". However, it is not a hard-and-fast rule, but depends on whether there is a precedent for that spelling or else whether the hyphen helps to clarify relationships that are otherwise ambiguous. Also, notice that the modifying noun becomes singular[*]. The compound cardinal directions are not hyphenated: northeast, southwest.

In a familiar example, we see the problem that could exist, that is, if it were not so familiar and if the first formulation weren't redundant to start with (!):

  • "long-time frame observation" is an observation of frames over a long period of time (better without the second part of the hyphenated phrase, obviously); or "long time-frame observation" where the observation insists on being within a specific, defined frame. To be honest, in general English, there is no discernible difference between the two, as both would be understood as "a very long observation", but as it is used so often in scientific articles, there must be a reason for the specific terms here: "time frame" for one.
  • Another example of this might be: "The local limb slope", where a non-expert might wonder if the limb is local ("local-limb slope") or if it is a limb of a slope ("local limb slope"). According to the rule, it must only be the second choice, since there is no hyphen.

The hyphen is particularly useful in complicated compounded phrases that also have these compounded noun phrases: e.g., "Closer inspection of our direct mass and luminosity function determinations reveals,..." Are we to inspect the direct mass more closely and also the luminosity-function determination? In these cases, as in so many, we may suggest the hyphen, which is a clue that there might be a reason for it in that situation. You are asked to consider its usefulness in that context; so when you feel it is clear for all astrophysicists, even those starting out in the specialty, then it need not be inserted in this case.


We often suggest that long sections in parenthesis be placed in the running text, where they are more appropriate than in, say, a footnote, as it directly relates to the subject at hand. In many cases, it can be connected by a comma followed by "which" or another relative pronoun. This does what some authors seem to want from the parentheses, so should be used instead, especially when there are already a lot of other parenthetical phrases in a section of the paper. If it is truly a side issue, then consider placing the information in a footnote. Otherwise, punctuate as if it is a full separate sentence, if it is at the end: e.g.

"We observed these stars for 24 hours (which did not include breaks to eat and sleep)." ⇒ "We observed these stars for 24 hours, which did not even include breaks for eating and sleeping."

You may use the same sentence but as a second parenthesis, punctuated as "We observed these stars for 24 hours. (This did not even include a break for eating and sleeping.)"

Avoid parentheses within parentheses, except when it is part of a formula. This includes the year in a reference that is placed in parenthesis, where we also prefer no comma between the name and year, but do expect the full stop after "et al.": (Johnson et al. 1999). When the name is in the text, then only the year is placed in parenthesis.

3.2 Capitalization and abbreviation

  • A&A asks you to capitalize only the first word of the title and subtitles, with the exception of proper nouns. Abbreviations are to be avoided in titles, unless they are very common ones such as cardinal directions (NE), some star names, or chemical terms; when possible, please write them out.
  • Like other journals, A&A asks you to remain in the formal register; that is, do not contract as in "don't" or "can't", while the second is one word: "cannot".
  • Follow the Instructions to Authors about capitalizing and abbreviating numbered references in your sentences, such as Fig. 1, Sect. 2, Eq. 3, or even Col. 4. When possible, use the plural for multiple items: "Figs. 2-4" or "Eqs. 5 and 6". "Table" is never abbreviated, although it is capitalized when followed by its designated number, while no word is abbreviated at the beginning of the sentence. Also, when any of these words are not followed by a number or letter indication, then it is treated as a normal noun that is not capitalized.
    Example: "This argument can be found in the next section, where Eqs. 5 and 6 are explained."
  • CAPITALIZE all adjectives and verbs formed from proper names, such as Poissonian or Compton, no matter how familiar it has become: Newtonian. One of few exceptions to this is "cartesian".
  • Use the LOWER CASE when introducing abbreviations and acronyms. The words that make up the introduced acronym are not capitalized unless either (i) a word is a proper name or (ii) the acronym does not use the first letters.
    Examples: star formation (SF), Atlantic Ocean (AO), the Galactic center (GC), HIgh-Precision PARallax COllecting Satellite (HIPPARCOS)
  • Use the lower case for the full names of chemical elements and for the cardinal directions: oxygen, southeast.

4 Verb tenses, plural/singular nouns

4.1 Verb tenses

The present tense

The present tense is used for statements of fact and general truths, for a set of steps in a method (not for the steps in testing), and for results, discussion, and conclusions that are set out in the paper itself. We do accept the present perfect and present simple for the work of others when the paper is cited, which comes from etiquette learnt for this situation. It must be consistent, however, and should avoid any time tags that contradict that tense choice. To be consistent, avoid using the present for your work and then the past tense for others' work in their papers, because it may suggest theirs is wrong.

The present perfect

Using the present perfect implies that the situation, even the action, is still going on, so not completed. It can also be used to put strong emphasis on how the situation has changed just this instant, usually with the negative: "I've never read such a fine article as this one." This problem occurs because of interference from other languages that use it for a finished, completed action, so we usually take this use as intending the simple past in English. However, we can obviously be mistaken in some cases. It is, however, true that most English style moves quickly out of the present perfect and avoids using it throughout a full paragraph in sentence after sentence, unlike in other languages. It is perceived as wordy.

The future

The future is expressed in English with either the present simple or the verb "will" and the infinite. When referring to work that follows in the same paper, use the present simple as appropriate to the immediate and certain future, while the classical form with "will" is used for future work after this article or for predicted events; it is used for events that are relatively certain, otherwise one of the conditional forms might be needed. "We explain our method in Sect. 2." vs "Once these stars have been observed, they will be analyzed using the new method."

Active vs. passive voice

Scientific language tends to use the passive, especially when talking of work done in a team; however, this has changed with time, so that A&A encourages authors to use the more personal and active forms when possible. Best for style is to vary the two and to use the active when the passive requires many more words.

Example: "The fact that such observations can lead to accurate results is demonstrated by our analysis."
⇒ "Our analysis demonstrates that such observations lead to accurate results."

4.2 Nouns: plural or singular

Some nouns can be either singular or plural depending on their context, although each has a preferred number.

NUMBER When you are referring to a lot of individual things, use the plural form, e.g., "A number of stars were found in our last observing run." But you must say "The total number of stars is ..." The sense in the second example is clearly singular with `total' emphasized, and here the normal meaning of `number' comes into play (=a sum total of things) as opposed to the rule above. You choose the number by your meaning, in other words. When "a large number of" means exactly the same as "many", then it must be plural.

MAJORITY `Majority' and `variety' follow the same rule as `number', although the sense of the word is the determining factor: do you mean it as a single entity or as a group of individuals? PLURAL: "The majority of scientists hope the agency will raise the number and amount of grants." SINGULAR: "The overwhelming majority still votes for amnesty."

STATISTICS Statistics is usually plural with some exceptions: "The statistics for our sample of stars are found in Table 1." If you want to make it singular in this meaning, then use "set of statistics". When referring to the study of statistics, then it is singular, but this is a rare use in astrophysics.

DATA Like other scientific publications, A&A remains `purist' by asking for the plural usage[*]. If you mean a single one, use "data point" instead of "datum".

5 Sentence structure and word order

5.1 Paragraphing

We do not usually have time to deal with the most effective way to develop an idea in sentences and paragraphs, being more concerned with more basic English problems related to clarity, but it is a concern and will be addressed when it is clearly a problem in any article. However, there are times we will make suggestions for paragraph breaks or ask an author to combine a single sentence that is swimming alone with one of the neighboring paragraphs. Otherwise, the best choice for paragraphs, as for sentences, is to aim for variety in length, if possible. Too many of the terse 2 to 3 sentence paragraphs in a row leads to monotony and a lack of transition or logical movement within a section, which is just as true for a series of short simple sentences in a paragraph. Paragraphs that are either too long or too short can be a problem for different reasons, with different solutions[*]. Each paragraph should have its own focus that is introduced in the first sentence and that includes some brief transition phrase from the preceding paragraph or else a clear connection to the topic of the whole section. This topic sentence should then be followed by two or more other sentences that develop and prove that idea, i.e., the standard expository paragraph.

5.2 The English default structure

The English declarative sentence has its main ("default") structure of subject, predicate (verb phrase), and objects of the action. It can be varied, if there's a reason, but should be used as often as possible. Other elements, such as adverbs, have a recommended order that you probably learned in early English classes, as for most of all this. Here, though, we mention those kinds of errors that we see often and that lead to either ambiguity or else to awkwardness, at least in the native-speaker's experience. Avoid separating the subject from its predicate (the main action/verb of the sentence): e.g. "The author, after revising the English, submitted his article." becomes "After revising the English, the author submitted ...".

5.3 Inverting this word order

Word order is often awkward in papers we see and must follow certain rules. Mostly, there must be a good reason for it, the least of which is variety, because there are many other ways to begin with something besides the subject, due to all the subordinate clauses available or adverbial phrases to introduce the sentence. If for some reason the complement to the verb comes first with the subject last, then there should be no punctuation to interrupt it for all are part of the main sentence, and it is even more confusing when this inverted sentence is interrupted by a subordinate clause. EXAMPLE: "Especially appealing is the study of its stellar winds."⇒ "Study of its winds is especially appealing". Unless this comes at the end of a rhetorical list we seldom see in scientific writing, then there is no reason for this inversion and the only improvement needed to the second version is to perhaps get rid of the 'of' phrasing: "Studying its winds is ..."

5.4 The direct object

It goes immediately after its verb with rare exceptions, and should not be separated without a very clear reason: "The star's image shows clearly the alignment." ⇒ Use either "clearly shows" or "shows the alignment clearly." Avoid interjecting long subordinate phrases as adverbials between the transitive verb and its direct object or in the middle of any clause, for that matter. And of course the transitive verbs should always have a direct object, with the most familiar problems "to allow", "to enable", and "to permit".

"This program allows to analyze the data" can be solved in 3 ways:

(i)   "This program allows us to analyze the data",
(ii)  "This program allows the data to be analyzed", or
(iii) "This program allows analysis of the data".

Several adverbs go before the verb: "only" and "also" are 2 familiar examples. But there are many preferred places for different grammatical forms, as in all languages, so if one has been corrected, please check a more basic grammar guide. If you felt that there was a reason for moving from the normal order, then perhaps something else in the sentence kept this emphasis from being clear as we were reading.

5.5 Parallel structure

Parallel structure is essential for avoiding ambiguity in compounded phrasing, whether in a list or between two longer sections of a sentence (See `Parallelism' in style guides). The compounded (or listed) items should share the same part of speech or syntax and all have the same grammatical status.


"The data were prepared analytically and by the Smith method (2001).")
⇒ "The data were prepared with an analytical method and by the Smith method (2001)" (or even better, if true, "The data were analyzed by the Smith method (2001).")

"It is best to use alternative methods because of the obscured point of view and because this is always a good idea in astronomy." (mixing a noun with a full clause))
⇒ "It is best to use alternative methods because the point of view is obscured and because this is always a good idea in astronomy."

Many elements are often combined in lists in the very long sections with details of scientific work and results. The rule is to make sure that the related items in the list maintain the same part of speech and syntax, as said, which includes repeating the preposition or obviously reusing the structure of the first in the others. When faced with several lists in one sentence (even compounding within lists), the logic becomes clear, for otherwise the reader cannot sort out which goes with which.

5.6 Unambiguous reference

Although it happens to the best of us, it is rare that we need to remind writers in A&A to check that an antecedent is clear in normal sentences. It does occur, however, in more complicated constructions, so the following rules were set up to avoid creating ambiguity and awkwardness in reference.

5.6.1Subordinate clause: THAT vs WHICH

In scientific journals, we prefer that the relative pronoun form of THAT is used for all restrictive connections and always without a comma, while WHICH is used only when the information following is added and not essential (non-restrictive) to the main idea of a sentence, something many are tempted to put into parenthesis, for instance, and is therefore always introduced with a comma after the preceding word[*]. See also page [*].

5.6.2 Subject of a subordinate clause: Dangling modifiers

And of course make certain that the subject of a subordinate phrase is really the same as the subject of the sentence ⇒ to avoid the "dangling modifier" that can be amusing at times: "Having studied the spectra, the 2 galaxies were approaching each other" ⇒ "Our study of the spectra showed that the 2 galaxies were approaching each other." Any other form is ambiguous. Avoid gerunds unless used as a noun phrase alone or in a prepositional phrase: e.g. "Studying stars is my hobby"; "After having read the ..., I ...".

6 Clarity and precision

In English, it is a stylistic virtue to be concise and to use the precise phrasing for an idea, while in science anything that is precise and clear is a necessary virtue, so that on this they coincide. In scientific writing, however, many wordy constructions have developed for various reasons and can be tolerated until too many of them combine to cloud the meaning. Likewise, poetic language and puns that work so well in other disciplines should be avoided in scientific articles as much as possible, especially when so many non-native speakers cannot appreciate them. On the other hand, some metaphors have entered into the terms of some specialities and other expressions are so common that they have become clear to close colleagues, perhaps even to the whole community. As language editors, we consider the astronomer from other specialities and other languages as much as possible in our suggestions[*]

Active phrasing

One way to do this is to aim for ACTIVE PHRASING as often as possible for several reasons, such as clarity, lively style, avoidance of too many `of' preposition phrases and "-tion" nouns. We look for any overuse of abstract nouns where the original verb form is more appropriate: "the estimation of x is ..." should be "estimating x is... ⇒ " We observe the planet by the detection of the stellar light it reflects" ⇒ "We observe the planet by detecting the stellar light it reflects" or even better ⇒ "We detect the planet by the stellar light it reflects." Considering that science requires these nouns, using more than is required means that it quickly becomes too abstract and wordy.

6.1 Indirect introductory phrasing

Indirect introductory phrasing should be used sparingly by the same token, as in the following examples.

  • Please avoid "It is worth stating that" or "We want to stress that" most of the time, if not always. In most cases it takes away from the strength of the assertion that follows, and is understood at any rate.
  • Avoid "we hope", "we wish", "we believe", etc. Even "We can see that ..." or "We think that ..." are already assumed by the reader, so are not useful.
  • Do not start a sentence with "concerning" or "with regard to": e.g., "Concerning the value of the frequency, we have investigated whether stars release ..." should be "We have investigated the value of the frequency at which stars release ..."

6.2 Avoiding ambiguity

Avoid ambiguous wording whenever possible. One notorious example is the connector "and", which in English is used too often for the more precise connector that is meant: "Divide and conquer" for "Divide, then conquer". The most obvious source of ambiguity comes from words that have more than one meaning or use, especially for connectors that are also used as adverbs, prepositions, and adjectives:

&bull; Like do you mean `such as'? or `similar to'?
&bull; As do you mean `because' or `while' or `during'?
&bull; Since do you mean `because' or `after which'?
&bull; While do you mean `whereas' or `during'?
&bull; So do you mean `therefore' or `meanwhile' or ?
&bull; Quite do you mean `very'? or `somewhat'?
&bull; Rather do you mean `instead'? `very'? `somewhat'?
&bull; Further do you mean `more'? `another'? `again'? `an extended'?
&bull; Such do you mean `this sort of'? `very much'? `these'? etc.
&bull; Few do you mean `very few' or `a few' or ?

Or from words that are close in sound, and often in meaning:

  • insure/assure/ensure
  • than/then
  • affect/effect/impact
  • relative to/compared to/with
  • respect to
  • comprise/consist of/be composed of
  • In contrast to/contrary to/opposed
  • to/compared to

Another major source of ambiguity is reference confusion (see Sect. 5.6), but also simply the use of too many words where a simpler phrasing is more appropriate because clearer. Likewise, non-native writers in English are not able to sense when a longer phrasing is appropriate or not, not that all native English writers do it well all the time either. Some areas where problems arise regularly in our experience follow. The first and easiest is to avoid any sexist or hemispheric phrasings such as "Summer 2005" (give the months rather), and if you do not know the referee's name then please acknowledge "her/his" or "the" useful comments, not merely "his". This occurs less in astrophysical writing, but please try to avoid using "American" alone when you mean "North American" or from the "United States of America", In general, try to use the fewest number of words possible, which often makes your ideas clearer, as long as the reader has a better chance of understanding your text. However, too much compactness can also cause confusion, as the connecting words, especially prepositions, have been removed. This happens a lot in scientific compositions of nouns modifying other nouns to avoid using the prepositional phrase with `of': "a theory of how stars are formed" becomes "a star-formation theory".

As an example of compacting too far, writers often leave off the 'that is' in modifying phrases and do so quite correctly, but it can also go too far, so we may suggest putting it back in to avoid ambiguity or for clearer style: "a theory more interesting than the facts") ⇒ "a theory that is more interesting than the facts".

6.3 Avoiding redundancies

These are examples of using two words that both mean, or at least imply, the same thing. They are wordy, though many have entered colloquial language (e.g., `slim and trim'). Ones that we have found during our editing include:

  • coupled together ⇒ coupled
  • In the obtained results ⇒ results
  • Determine the point of onset of... ⇒ determine the onset of
  • Decreases down ⇒ decreases

6.4 Avoiding vague qualitative descriptions

  • A good example here is "rather small". In this case, compare it with something larger.
  • In English, if not most languages, "very important" means the same thing as "important", and even less when "very" is overused.
  • Likewise, watch out for undermining absolutes: if only "partly true", then which part is true and which not (?); "somewhat consistent" ("consistent" is absolute, so it cannot be partly so).
  • Or else "in fact" or "the fact that" need to be avoided as often as possible; make certain it is a fact.
  • "In any case" and some other familiar filler expressions cloud scientific writing, so use them when you actually mean it. This example does not mean "Oh well!" in writing, unlike in discourse, or the more recent Americanism "Whatever!" If there are two possible cases being discussed, use "in either case".

6.5 Avoiding wordy constructions that mean the same as the direct one

"In order to" can usually be shortened to the infinitive alone "to" plus the verb.

"On/of the order of" in the sense of "approximately, about, roughly" is sometimes the only form used, and it is used often, so that it becomes awkward. It also sounds so much like "order of magnitude" that it gets confused in the writing and, probably, understanding of either. Try to use the other forms of approximate measurements as often as possible.

  • X is of particular importance ⇒ X is particularly important
  • X is only of an approximate nature ⇒ X is only approximate
  • To detect the presence of an atmosphere ⇒ to detect an atmosphere
  • To perform an identification ⇒ to identify
  • Concerning the explosion, its effect is ... ⇒ The effect of the explosion is ...
  • The intersection of x and y occurs ⇒ x intersects y
  • We aim at estimating (If not in the abstract) ⇒ We estimate
  • Make a comparison with ⇒ to compare .... (Likewise other noun versions of active verbs, when not needed for meaning)
  • Show strong indications of something ⇒ to indicate something strongly
  • Is in contradiction with ⇒ contradicts
  • Is in agreement ⇒ agrees with
  • Before proceeding further, it is worth commenting at this point that we have studied the ... ⇒ We have studied the ...

And finally, stay away from the double negative in favor of a direct, affirmative statement: "This result is not unlikely" can be either "This result is likely" or "This result is possible". Notice that the "litotes" format is slightly ambiguous, because it does not indicate the degree precisely, except for what it is not.

6.6Transitional phrases

are useful, but when they only add words or repeat themselves, they need to be avoided: Avoid "actually", "in fact", "moreover", "indeed", etc., or use only when they help clarify relations rather than muddle them. Likewise, "hence' can be very useful in the right context, but when overused becomes useless and loses its rhetorical power. Once or twice a paper makes sense, but not once or twice a page or more often. Even if tempted to place one of its synonyms, be aware that overuse of several of these in a row begins to seem odd, too; just as using a string of sentences all containing indicators of contrast (but, however, in contrast, etc) seems like the writer is arguing with her/himself.

7 Some frequent corrections

• Overuse of "SUCH" for "THIS"

E.g., "such stars" after already referring to specific ones ⇒ "these stars" "SUCH" is not the normal demonstrative article, and it is not used like this in most contexts in the non- English-speakers' papers. When this meaning of "such" is used more than 1/3 as often as the equivalent "this", then it needs changing except for the case of "this sort of" or "this kind of" only. Also, watch out!-"such a" can be insulting in some contexts when the author maybe meant only "this": e.g., "...(Jones 1994). Such an article is ..." It is also ambiguous is several instances, and the author will be asked to choose either "this" or "this kind of" to eliminate the confusion for both English native and non native readers.

• Overuse of "FURTHER"

"Further" being used exclusively instead of the standard "more" or "another/other" or "earlier/former" or even "then" in a sequence (!), e.g., "further studies" for "more studies". Each of these means something slightly different from the others, and sometimes means something truly different, and "further" does not always mean what they usually mean. Examples:

  • adds a further layer to ⇒ adds another layer to ...
  • We did further research ⇒ We did more research

It means "more extended" not simply "a greater number of" as so often seen.


"these/this latter X" ⇒ Either "these/this X" or "the latter X", though the first is preferred. "The latter" only for 2, `last' is for more than 2, even when you mean the last 2 of only 3.

• Overuse of "TOGETHER WITH" and "AS WELL AS"

which are otherwise very useful structures in English. Note that only "and" is used after "both", and never "as well as", as in: "Both X as well as Y are ..." ⇒ "Both X and Y are ..."

• Overuse of "BEST"

rather than the precise word for what is meant. This tends to be younger authors, and not just French ones. We offer them a choice of synonyms of "best", all except "favorite": precise, useful, clear, most likely, etc.

High/low vs. large/small

The high/low vs. large/small or strong/weak problem: the lefthand column gives the attribute, the righthand one the words that use them. NB, some show up in two places.

  • High or low: Most words that are typically indicated by up/down graphs: Value, rate, redshift, degree, temperature, metallicity, luminosity, speed, velocity, contrast, energy, frequency, level, density, shear, extinction, pressure, eccentricity, inclination, proportion, abundance, fractionation, flux, background (or strong?)
  • Big/large or small: Scale, correlation (?), broadening (?), opacity, amplitude, mass, momentum, uncertainties, diffusivity
  • Can be either high/low or large/small: It depends on the emphasis: number, frequency, dispersion (both?), coefficients (or only large?)
  • Short or long: Time, length, timescale
  • Strong or weak: Pulse, current, correlation, gradient, flow, shear, dependence, velocity field, asymmetry, contrast, constraint, turbulence, instability, acceleration, anisotropy
  • Tight or loose: Often the same as "strong/weak": relationship, correlation

&bull; Other frequent corrections

  • "Like for example" ⇒ "Such as"
  • "Non negligible" ⇒ "Significant" or "of low significance" (avoid litotes)
  • Both "more metal-poorer" and "metal-poorer" are found in ApJ and MNRAS, so both are correct but the second is better when it modifies a plural noun so is ambiguous. However, in many cases it is better to rephrase to "is richer/poorer in metal(s)".

Appendix A: References

Some of the available guides for scientific and technical writing that offer a wealth of examples and references along with clear explanations are

Other useful sources are
  1. the latest edition of The Chicago Manual of Style (use their online search tools that give personal commentary by the editors on different points with lots of examples. http://www.press.uchicago.edu/Misc/Chicago/cmosfaq/tools.html
  2. http://dictionary.cambridge.org Cambridge dictionaries on the web
  3. Merriam-Webster at either http://dictionary.cambridge.org or http://www.websters-online-dictionary.org/definition/.
  4. Online encyclopaedias such as: (i) Wikipedia, especially its collection of pages under the headings of Natural Sciences, Mathematics, Technology, http://en.wikipedia.org/wiki/Wikipedia:Browse or (ii) Answers.com http://www.answers.com/topic/accretion-disc with 'accretion disk' as the example here. This one uses several dictionaries and encyclopaedia articles, so may use several spellings of any words with a choice.
  5. William Strunk & E.B. White The Elements of Style on 'Bartleby.com', especially their sections of common usage errors at: http://www.bartleby.com/141/strunk3.html or else useful general English guides from Hartford Community College/ Webster with a user-friendly portal at http://grammar.ccc.commnet.edu/grammar. Another resource could also be Fowler's The King's English also on Bartleby.com, but watch out for his irony and more complicated explanations compared to Strunk & White.
  6. Mary K. McCaskill. "Grammar, Punctuation, and Capitalisation: A Handbook for Technical Writers and Editors". Langley Research Center (NASA SP-7084) at: http://www.sti.nasa.gov/sp7084/contents.html.

Additional references on UK/US Spelling Conventions

If interested in less scientific differences, take a look at: Tripod.com's "US2UK"[*] or Krysstal's page of the differences[*]. Meanwhile, if you consider you are writing in another English dialect than either UK or US variants, then please let us know. If we cannot set our own spell checks on your file, however, then please include a list of what you consider the differences to be, which we can check if we feel it necessary: for instance, see Wikipedia's pages (gateway at http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style#National_varieties_of_English) on this concern, including the following statement on Australian English: "Both -ise and -ize are accepted, as in British English, but `-ise' is the preferred form in Australian English by a ratio of about 3:1 according to the Australian Corpus of English" (on http://en.wikipedia.org/wiki/Australian_English).

Copyright ESO 2010

English Editing at Astronomy & Astrophysics

This short language guide is designed to help you meet A&A standards when you are preparing your paper and to understand the changes that the A&A language editors (LEs) make to your manuscript (MS). Please see the editorial on language editing for a more extensive explanation of our editing goals (A&A 490, E19).

1.1 Scope of this language guide

This guide is based on the kinds of changes the LEs recommend most often in A&A papers, so it does not pretend to be a complete English language guide. For instance, common language errors that we only see at times are not included in the explanations because they are explained in other general grammars, dictionaries, and handbooks.

The LEs strive for consistency in editing those MSs selected for language editing. Nevertheless, there will always be variations in the English found in the Journal as a whole. This occurs because there is often more than one way to construct a phrase or sentence or even to correct a grammar problem.

A few matters that are not directly language concerns, but rather conventions in use at A&A are explained in the following sections.

1.2 A&A house style

The following A&A conventions are enforced by LEs:

  • A&A aims to maintain a formal register (style) in the body of the paper.

    This includes the following:

    • Do not contract two words: replace “don’t”, “can’t”, “won’t”, “it’s” by “do not”, “cannot”, “will not”, “it is”, etc.
    • Avoid addressing the reader directly in the imperative:
      • “Note that the data were...”
      • “The data were...”
      • “We would like to point out that the data were…”
      • "We note that…”.
    • Write out figures when lower than eleven and not directly used in a measurement with the unit following: e.g., “five years” and “5 yr”.
    • Use the full terms for many abbreviations when in the running text, such as “e.g.”, “i.e.”, or “w.r.t”. The handy signs used in note-taking and between colleagues in meetings (e.g., slashes, the ampersand) should be avoided in the main text.
      • “mounted at the ESO/VLT@UT1 telescope”
      • “mounted on the Unit 1 telescope (UT1) at ESO's VLT”.
  • Only the first word of a heading should be capitalized, along with proper names.

    For example, “Sect. 5. Discussion and conclusions”, and abbreviations should be avoided. Also see Sect. 5.3.1. for other examples.

  • Italics for indicating emphasis are discouraged.
  • Date format needs to be consistent within the text of a single paper.

    The following choices are allowed:

    • 4 January 2004 or 4 Jan 2004; January 4, 2004 or Jan 4, 2004;
    • 2004 January 4 or 4 Jan 2004.

    We ask that the cardinal endings be left off for dates because it is informal style and that the month be written out, since 4-1-2004 is ambiguous between cultures, and it too is informal inside the text.

  • The tilde symbol (~) is used to mean “approximately” before measurements (~ 5 yr) but not before actual words.

    The tilde is useful to avoid wordier synonyms like “on the order of”, which should only be used for measurements with figures, not for a general noun (“on the order of 10 Gyr” not “on the order of the age of the star”). The related symbol “≈” should be reserved for mathematical expressions, rather than used as an alternative to the tilde.

1.3 Adjustments to the Abstract and captions

1.3.1 Abstract

The LEs revise any incomplete sentence used after a heading.

  • “Aims. Investigate stars.” should instead be written as
  • “Aims. We investigate stars.” or as
  • “Aims. We aim to investigate stars.”

Since abstracts are supposed to be self-contained, LEs suggest substituting most citations of earlier work with other wording.

  • “Two transverse profiles are distinguished, one being the generalized Epsteli> distribution (profile E) and the other (N) proposed recently in Smith et al. (2012)”
  • “Two transverse profiles are distinguished that we call Profiles E and N.”

The required sections are Aims, Method, and Results, even if you choose not to use the headings. If the content of a section is missing or if it contradicts the headings, LEs point it out and suggest an adjustment. See the editorial on Abstracts from when A&A introduced the structured abstract. (A&A 441, E3)

1.3.2 Captions to tables and figures

In line with A&A conventions for captions and with the “Paper organization” page for authors [http://www.aanda.org/for-authors/author-information/paper-organization], the LEs ask you to remove any article (A, An, The) at the beginning of the caption, legend details in the body of the text that repeat information in the caption, or any discursive language or information (e.g., results) that do not directly explain symbols in the figure.

We also adjust the caption to resemble the expected style: e.g., the first phrase should not be a full sentence, or notes to tables should resemble footnote style, not that of the running text.

1.4 Suggested resources

1.4.1 Guidebooks from other scientific disciplines and laboratories

These guides follow the same principles as A&A, so you can use them for most questions, even if their examples come from their disciplines. These include

  • CHEMISTRY: The ACS Style Guide: A Manual for Authors and Editors, Second Edition, edited by Janet S. Dodd. Its sections are: Getting Started, Writing Style and Word Usage, Components of a Paper, Types of Presentations, Advice from the Authorities.
  • BIOLOGY, the biology department at Columbia University: Writing a scientific research article [http://www.columbia.edu/cu/biology/ug/research/paper.html] Its main sections are found under “Format for the paper” and “Edit your paper!!” Both of these repeat in detail what language editors are looking for when editing your papers, so you can see there that we are not being any more rigorous than others are.
  • NASA – Langley Research Laboratories guide for authors presenting reports by Mary McCaskill [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900017394.pdf] This is the fourth NASA URL found for this resource, so if it does not work (again), try to find it by a search engine using the title and author; otherwise, consider the following list of English for science resources to complement those here.
  • Guide to Grammar and Writing is a resource by Capital Community College in Hartford Connecticut. [http://guidetogrammar.org/grammar/]
  • The latest edition of The Chicago Manual of Style, Chicago University Press. This extensive manual is used by most scientific communities in the United States, including psychology. It may be too technical and detailed, when most of what you need is on the A&A site. The book itself is bulky, but it is possible to subscribe to it online to access all its sections (including the style guide) and even to ask specific questions of its staff of editors.

1.4.2 Other online resources for scientific writing and writing in general