mufti vs plain clothes

mufti and plain clothes both are nouns.

Word	Noun	Adjective	Verb	Adverb
mufti	Yes	No	No	No
plain clothes	Yes	No	No	No

As nouns, plain clothes is a hypernym of mufti; that is, plain clothes is a word with a broader meaning than mufti:

mufti: civilian dress worn by a person who is entitled to wear a military uniform
plain clothes: ordinary clothing as distinguished from uniforms, work clothes, clerical garb, etc.

Other hypernyms of mufti include civilian clothing, civilian dress, civilian garb.

mufti (noun)	plain clothes (noun)
civilian dress worn by a person who is entitled to wear a military uniform	ordinary clothing as distinguished from uniforms, work clothes, clerical garb, etc.
a jurist who interprets Muslim religious law