retain vs keep back

retain and keep back both are verbs.

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

As verbs, retain and keep back are synonyms defined as:

retain and keep back: secure and keep for possible future use or application

Other synonyms of retain include hold, hold back.

retain (verb)	keep back (verb)
keep in one's mind	prevent the action or expression of
secure and keep for possible future use or application	hold back; refuse to hand over or share
allow to remain in a place or position or maintain a property or feature	secure and keep for possible future use or application
hold back within