imprison vs put behind bars

imprison and put behind bars both are verbs.

Word	Noun	Adjective	Verb	Adverb
imprison	No	No	Yes	No
put behind bars	No	No	Yes	No

As verbs, imprison and put behind bars are synonyms defined as:

Other synonyms of imprison include gaol, immure, incarcerate, jail, jug, lag, put away, remand.

imprison (verb)	put behind bars (verb)
lock up or confine, in or as in a jail	lock up or confine, in or as in a jail
confine as if in a prison