rapper vs singer

rapper and singer both are nouns.

Word	Noun	Adjective	Verb	Adverb
rapper	Yes	No	No	No
singer	Yes	No	No	No

As nouns, singer is a hypernym of rapper; that is, singer is a word with a broader meaning than rapper:

Other hypernyms of rapper include vocaliser, vocalist, vocalizer.

rapper (noun)	singer (noun)
a device (usually metal and ornamental) attached by a hinge to a door	a person who sings
someone who performs rap music