diphthongise vs British spelling

diphthongise is not a noun while British spelling is a noun.

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

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

diphthongise (verb)	British spelling (verb)
change from a simple vowel to a diphthong