# Units and dimensions¶

Support for dimensional quantities is a fundamental (and essential) feature of NeuroML, backed up by support for units and dimensions in LEMS.

The basic rules are:

• specify the dimensions of quantities in LEMS

• use compatible units defined in the NeuroML schema in NeuroML models.

The main motivation for this is that fundamental expressions for defining a model are independent of any particular units. For example, Ohm’s law, V = I * R relates to quantities with dimensions voltage, current and resistance, not millivolts, picoamps, ohms, etc.

Users can therefore use a wide range of commonly used units for each dimension defined in the standard unit and dimension definitions of NeuroML 2 without worrying about conversion factors.

• when plotting data using NeuroML/LEMS using the Line component, users can use the scale parameter to convert quantities to other units.