hold on vs cling

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

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

As verbs, cling is a hyponym of hold on; that is, cling is a word with a more specific, narrower meaning than hold on:

Other hyponyms of hold on include latch on, hang, clasp.

hold on (noun)	cling (noun)
	fruit (especially peach) whose flesh adheres strongly to the pit

hold on (verb)	cling (verb)
be persistent, refuse to stop	come or be in close contact with; stick or hold together and resist separation
stop and wait, as if awaiting further instructions or developments	hold on tightly or tenaciously
hold the phone line open	to remain emotionally or intellectually attached
hold firmly
retain possession of