hearing aid vs deaf-aid

hearing aid and deaf-aid both are nouns.

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

As nouns, hearing aid and deaf-aid are synonyms defined as:

hearing aid and deaf-aid: an electronic device that amplifies sound and is worn to compensate for poor hearing

hearing aid (noun)	deaf-aid (noun)
a conical acoustic device formerly used to direct sound to the ear of a hearing-impaired person	an electronic device that amplifies sound and is worn to compensate for poor hearing
an electronic device that amplifies sound and is worn to compensate for poor hearing