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