British spelling vs agonising

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

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

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

British spelling (adjective)	agonising (adjective)
	extremely painful