## 9.3.5 The `units` section

The `units` section can be used to define new physical units for use within Pyxplot’s mathematical environment. Each line should take the format of

    <l_sing> \[ / <s_sing> \] \[ / <lt_sing> \]
       \[ / <l_plur> \] \[ / <s_plur> \] \[ / <lt_plur> \]
       : <quantity_name> = \[ <definition> \]

where

`l_sing` | is the long singular name of the unit, e.g. `metre`.
`s_sing` | is the short singular name of the unit, e.g. `m`.
`lt_sing` | is the singular name of the unit to be used in latex.
`l_plur` | is the long plural name of the unit, e.g. `metres`.
`s_plur` | is the short plural name of the unit, e.g. `m`.
`lt_plur` | is the plural name of the unit to be used in latex.
`quantity_name` | is the physical quantity which the unit measures, e.g. `length`.
`definition` | is a definition of the unit in terms of other units which Pyxplot already recognises, e.g. `0.001*km`. The syntax used is identical to that used in the `unit()` function.

For example, a definition of the metre would look like

    metre/m/m/metres/m/m:length=0.001*km

Not all of the various names which a unit may have need to be specified. If plural names are not specified then they are assumed to be the same as the singular names. If short and/or latex names are not specified they are assumed to be the same as the long name. If the definition is left blank then the unit is assumed to be a new base unit which is not related to any pre-existing units.