hold on vs wait

hold on is not a noun while wait is a noun.

Word	Noun	Adjective	Verb	Adverb
hold on	No	No	Yes	No
wait	Yes	No	Yes	No

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

Other hypernyms of hold on include await, expect, look.

hold on (noun)	wait (noun)
	the act of waiting (remaining inactive in one place while expecting something)
	time during which some action is awaited

hold on (verb)	wait (verb)
be persistent, refuse to stop	look forward to the probable occurrence of
stop and wait, as if awaiting further instructions or developments	serve as a waiter or waitress in a restaurant
hold the phone line open	stay in one place and anticipate or expect something
hold firmly	wait before acting
retain possession of