roof vs ceiling

roof and ceiling both are nouns.

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

As nouns, roof and ceiling are synonyms defined as:

Other synonyms of roof include cap.

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

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