square metre vs British spelling

square metre and British spelling both are nouns.

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

square metre (noun)	British spelling (noun)
a unit of measurement for area, defined as the area of a square with sides of exactly 1 metre; a centiare is 1/100th of an are	English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')