British spelling vs usable

British spelling is a noun but usable is not a noun.

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

British spelling (noun)	usable (noun)
English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')

British spelling (adjective)	usable (adjective)
	convenient for use or disposal
	fit or ready for use or service
	capable of being put to use