ceiling vs roof

ceiling and roof both are nouns.

Word	Noun	Adjective	Verb	Adverb
ceiling	Yes	No	No	No
roof	Yes	No	Yes	No

As nouns, ceiling and roof are synonyms defined as:

Other synonyms of ceiling include cap.

ceiling (noun)	roof (noun)
the overhead upper surface of a covered space	a protective covering that covers or forms the top of a building
(meteorology) altitude of the lowest layer of clouds	protective covering on top of a motor vehicle
maximum altitude at which a plane can fly (under specified conditions)	an upper limit on what is allowed
an upper limit on what is allowed	the inner top surface of a covered area or hollow space

ceiling (verb)	roof (verb)
	provide a building with a roof; cover a building with a roof