retain vs keep up

retain and keep up both are verbs.

Word	Noun	Adjective	Verb	Adverb
retain	No	No	Yes	No
keep up	No	No	Yes	No

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

retain: allow to remain in a place or position or maintain a property or feature
keep up: lengthen or extend in duration or space

Other hypernyms of retain include prolong, sustain.

retain (verb)	keep up (verb)
keep in one's mind	prevent from going to bed at night
secure and keep for possible future use or application	keep informed
allow to remain in a place or position or maintain a property or feature	maintain a required pace or level
hold back within	keep in safety and protect from harm, decay, loss, or destruction
	lengthen or extend in duration or space