extemporisation vs British spelling

extemporisation and British spelling both are nouns.

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

extemporisation (noun)	British spelling (noun)
a performance given extempore without planning or preparation	English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')