morning dress vs frock

morning dress and frock both are nouns.

Word	Noun	Adjective	Verb	Adverb
morning dress	Yes	No	No	No
frock	Yes	No	Yes	No

As nouns, frock is a hypernym of morning dress; that is, frock is a word with a broader meaning than morning dress:

Other hypernyms of morning dress include dress.

morning dress (noun)	frock (noun)
a woman's informal dress for housework	a one-piece garment for a woman; has skirt and bodice
formal attire for men during the daytime	a habit worn by clerics
	a long, loose outer garment

morning dress (verb)	frock (verb)
	put a frock on