What does the prefix im in the word imprison mean?

The prefix "im-" in the Word "imprison" is a variant of the prefix "in-," which means "into" or "within." Therefore, in this context, "im-" indicates the action of putting someone "into" or "within" a prison or confined space. The use of this prefix changes the meaning of the base Word "prison" from simply a place of confinement to the act of confining someone within a prison.