British spelling vs square millimetre

British spelling and square millimetre both are nouns.

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

British spelling (noun)	square millimetre (noun)
English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')	a unit of area measurement equivalent to 1 millimeter in length multiplied by 1 millimeter in width.