femtometre vs British spelling

femtometre and British spelling both are nouns.

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

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