restrain vs hold in

restrain and hold in both are verbs.

Word	Noun	Adjective	Verb	Adverb
restrain	No	No	Yes	No
hold in	No	No	Yes	No

As verbs, hold in is a hyponym of restrain; that is, hold in is a word with a more specific, narrower meaning than restrain:

restrain: prevent the action or expression of
hold in: lessen the intensity of; temper; hold in restraint; hold or keep within limits

restrain (verb)	hold in (verb)
prevent the action or expression of	hold back; keep from being perceived by others
to close within bounds, or otherwise limit or deprive of free movement	lessen the intensity of; temper; hold in restraint; hold or keep within limits
restrict (someone or something) so as to make free movement difficult	close in
prevent (someone or something) from doing something