retention vs keeping

retention and keeping both are nouns.

Word	Noun	Adjective	Verb	Adverb
retention	Yes	No	No	No
keeping	Yes	No	No	No

As nouns, retention and keeping are synonyms defined as:

Other synonyms of retention include holding.

retention (noun)	keeping (noun)
the act of retaining something	the responsibility of a guardian or keeper
the power of retaining liquid	conformity or harmony
the power of retaining and recalling past experience	the act of retaining something