nm vs micromillimeter

nm and micromillimeter both are nouns.

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

As nouns, nm and micromillimeter are synonyms defined as:

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

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

nm (noun)	micromillimeter (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