singing vs sing

singing is a noun but sing is not a noun.

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

singing (noun)	sing (noun)
the act of singing vocal music
disclosing information or giving evidence about another

singing (adjective)	sing (adjective)
smooth and flowing

singing (verb)	sing (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