retain vs hold on

retain and hold on both are verbs.

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

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

Other hypernyms of retain include keep.

retain (verb)	hold on (verb)
keep in one's mind	be persistent, refuse to stop
secure and keep for possible future use or application	stop and wait, as if awaiting further instructions or developments
allow to remain in a place or position or maintain a property or feature	hold the phone line open
hold back within	hold firmly
	retain possession of