mum vs British spelling

mum and British spelling both are nouns.

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

mum (noun)	British spelling (noun)
secrecy	English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')
informal terms for a mother
of China

mum (adjective)	British spelling (adjective)
failing to speak or communicate etc when expected to