restrain vs keep back

restrain and keep back both are verbs.

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

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

Other synonyms of restrain include hold back, keep.

restrain (verb)	keep back (verb)
prevent the action or expression of	prevent the action or expression of
to close within bounds, or otherwise limit or deprive of free movement	hold back; refuse to hand over or share
restrict (someone or something) so as to make free movement difficult	secure and keep for possible future use or application
prevent (someone or something) from doing something