British spelling vs millimetre

British spelling and millimetre both are nouns.

Word	Noun	Adjective	Verb	Adverb
British spelling	Yes	No	No	No
millimetre	Yes	No	No	No

British spelling (noun)	millimetre (noun)
English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')	a metric unit of length equal to one thousandth of a meter