When specifying a dimension (e.g. in a footprint name) the units must always be provided:

When specifying areas or volumes, the coordinate order is X-Y[-Z], which is equivalent to width-height[-thickness].

When specifying multidimensional units (e.g. width x height x thickness) then the units only need to be appended once

Metric units are preferred, where appropriate

Linear dimensions should be specified in millimeters

Angular dimensions should be specified in degrees

Temperature should be specified in degrees Celsius