optimisation vs British spelling

optimisation and British spelling both are nouns.

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

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