chant vs sing

chant is a noun but sing is not a noun.

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

As verbs, sing is a hypernym of chant; that is, sing is a word with a broader meaning than chant:

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

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