sing vs singer

sing is not a noun while singer is a noun.

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

sing (noun)	singer (noun)
	a person who sings

sing (verb)	singer (verb)
make a whining, ringing, or whistling sound
divulge confidential information or secrets
to make melodious sounds
produce tones with the voice
deliver by singing