British spelling vs coincidentally

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

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

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

British spelling (adverb)	coincidentally (adverb)
	happening at the same time