deaf vs hearing-impaired

deaf is a noun but hearing-impaired is not a noun.

Word	Noun	Adjective	Verb	Adverb
deaf	Yes	Yes	Yes	No
hearing-impaired	No	Yes	No	No

deaf (noun)	hearing-impaired (noun)
people who have severe hearing impairments

deaf (adjective)	hearing-impaired (adjective)
lacking or deprived of the sense of hearing wholly or in part	having a hearing loss
(usually followed by `to') unwilling or refusing to pay heed

deaf (verb)	hearing-impaired (verb)
make or render deaf