How is the need for line memorization in theater actors similar to or different from the need for line memorization in film actors?

It is more critical for theater actors to have their lines firmly memorized because their performances are going to be live. With a TV or film actor, for the most part, they can ask for the line and retake the shot. There are a few live television shows but for the most part, things are recorded so while it is important for film actors, it is imperative for theater actors.