The function GetDimension(dim) returns the argument for a base dimension, and the product of powers of base dimensions for any other dimension.

$\mathrm{with}\left(\mathrm{Units}\right)\:$

Automatically loading the Units[Simple] subpackage

$\mathrm{GetDimension}\left(\'\mathrm{length}\'\right)$

$\mathrm{length}$

$\mathrm{GetDimension}\left(\'\mathrm{speed}\'\right)$

$\frac{\mathrm{length}}{\mathrm{time}}$

$\mathrm{GetDimension}\left(\'\mathrm{acceleration}\'\right)$

$\frac{\mathrm{length}}{{\mathrm{time}}^2}$

$\mathrm{GetDimension}\left(\'\mathrm{surge}\'\right)$

Error, (in Units:-GetDimension) a dimension with name `surge` does not exist

$\mathrm{AddDimension}\left(\'\mathrm{surge}\'\=\frac{\'\mathrm{length}\'}{{\'\mathrm{time}\'}^3}\right)$

$\mathrm{GetDimension}\left(\'\mathrm{surge}\'\right)$

$\frac{\mathrm{length}}{{\mathrm{time}}^3}$