sing vs chant

sing is not a noun while chant is a noun.

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

As verbs, chant is a hyponym of sing; that is, chant is a word with a more specific, narrower meaning than sing:

sing (noun)	chant (noun)
	a repetitive song in which as many syllables as necessary are assigned to a single tone

sing (verb)	chant (verb)
make a whining, ringing, or whistling sound	recite with musical intonation; recite as a chant or a psalm
divulge confidential information or secrets	utter monotonously and repetitively and rhythmically
to make melodious sounds
produce tones with the voice
deliver by singing