civies vs plain clothes

civies and plain clothes both are nouns.

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

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

civies: civilian garb as opposed to a military uniform
plain clothes: ordinary clothing as distinguished from uniforms, work clothes, clerical garb, etc.

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

civies (noun)	plain clothes (noun)
civilian garb as opposed to a military uniform	ordinary clothing as distinguished from uniforms, work clothes, clerical garb, etc.