Source:http://linkedlifedata.com/resource/umls/id/C1707683
NCI: Derived units of the International System of Units (Systeme International d'Unites, SI) are those formed by combining base SI units according to the algebraic relations linking the corresponding quantities. The names and symbols of some of the units thus formed can be replaced by special names and symbols which can themselves be used to form expressions and symbols of other derived units.