square millimetre vs British spelling

square millimetre and British spelling both are nouns.

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

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