nm vs micromillimetre

nm and micromillimetre both are nouns.

Word	Noun	Adjective	Verb	Adverb
nm	Yes	No	No	No
micromillimetre	Yes	No	No	No

As nouns, nm and micromillimetre are synonyms defined as:

nm and micromillimetre: a metric unit of length equal to one billionth of a meter

Other synonyms of nm include micromillimeter, millimicron, nanometer, nanometre.

nm (noun)	micromillimetre (noun)
a metric unit of length equal to one billionth of a meter	a metric unit of length equal to one billionth of a meter