A hypnotist is someone who hypnotizes people. That can be a stage hypnotist, who makes a show of it — volunteers doing silly things, forgetting a word — or, more quietly, anyone whose job is to bring on hypnosis. In careful talk, the clinic worker is more often called a hypnotherapist, because their aim is treatment, not a laugh. Everyday English still says hypnotist for both, and students will hear both. The word names the person who does the hypnotizing, not the state and not the treatment. Though actually, the stage picture is so strong that many people hear hypnotist and see a swinging watch, even when the real work is a calm voice in a quiet room.