come on vs start

come on is not a noun while start is a noun.

Word	Noun	Adjective	Verb	Adverb
come on	No	No	Yes	No
start	Yes	No	Yes	No

As verbs, start is a hypernym of come on; that is, start is a word with a broader meaning than come on:

Other hypernyms of come on include begin, commence, get, get down, set about, set out, start out.

As verbs, start is a hypernym of come on; that is, start is a word with a broader meaning than come on:

Other hypernyms of come on include get going, go.

come on (noun)	start (noun)
	the act of starting something
	a sudden involuntary movement
	a turn to be a starter (in a game at the beginning)
	the advantage gained by beginning early (as in a race)
	a signal to begin (as in a race)
	the beginning of anything
	a line indicating the location of the start of a race or a game
	the time at which something is supposed to begin

come on (verb)	start (verb)
occur or become available	take the first step or steps in carrying out an action
appear or become visible; make a showing	set in motion, cause to start
develop in a positive way	play in the starting lineup
start running, functioning, or operating	bring into being
move towards	get off the ground
	begin or set in motion
	get going or set in motion
	depart for someplace
	bulge outward
	move or jump suddenly, as if in surprise or alarm
	begin work or acting in a certain capacity, office or job
	begin an event that is implied and limited by the nature or inherent function of the direct object
	have a beginning, in a temporal, spatial, or evaluative sense
	have a beginning characterized in some specified way