nm vs nanometre

nm and nanometre both are nouns.

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

As nouns, nm and nanometre are synonyms defined as:

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

nm (noun)	nanometre (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