human face vs mouth

human face and mouth both are nouns.

Word	Noun	Adjective	Verb	Adverb
human face	Yes	No	No	No
mouth	Yes	No	Yes	No

human face (noun)	mouth (noun)
the front of the human head from the forehead to the chin and ear to ear	the opening of a jar or bottle
	the externally visible part of the oral cavity on the face and the system of organs surrounding the opening
	the opening through which food is taken in and vocalizations emerge
	an impudent or insolent rejoinder
	the point where a stream issues into a larger body of water
	an opening that resembles a mouth (as of a cave or a gorge)
	a person conceived as a consumer of food
	a spokesperson (as a lawyer)

human face (verb)	mouth (verb)
	express in speech
	articulate silently; form words with the lips only
	touch with the mouth