nm vs millimicron

nm and millimicron both are nouns.

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

As nouns, nm and millimicron are synonyms defined as:

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

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

nm (noun)	millimicron (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