British spelling vs mediaeval

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

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

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

British spelling (adjective)	mediaeval (adjective)
	relating to or belonging to the Middle Ages
	as if belonging to the Middle Ages; old-fashioned and unenlightened
	characteristic of the time of chivalry and knighthood in the Middle Ages