The AMUSE units module. The upper panel illustrates the use of the unit algebra module. (1) Definition of a scalar quantity using the | operator; (2) definition of a vector quantity; (3) use of units in functions; and (4) conversion of units. Lower panel illustrates the use of a converter between N-body units and SI. (1) defines a converter from units with G   =   1 (implicit), M_⊙ = 1 and AU = 1 to SI units; (2) conversion to SI units; (3) conversion from SI units.