muscle fibre vs British spelling

muscle fibre and British spelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
muscle fibre	Yes	No	No	No
British spelling	Yes	No	No	No

muscle fibre (noun)	British spelling (noun)
an elongated contractile cell that forms the muscles of the body	English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')