mouth vs roof of the mouth

mouth and roof of the mouth both are nouns.

Word	Noun	Adjective	Verb	Adverb
mouth	Yes	No	Yes	No
roof of the mouth	Yes	No	No	No

mouth (noun)	roof of the mouth (noun)
the opening of a jar or bottle	the upper surface of the mouth that separates the oral and nasal cavities
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)

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