A character drinks from a glass. In the next shot, the glass is full again. The audience notices. Continuity is the consistency of details across shots to maintain believability. It covers props, costumes, makeup, lighting, and action. If a character has a scar on their left cheek in one shot, it must be on the left cheek in the next. If the sun is setting in one shot, it cannot be high in the sky in the next. Continuity errors break the illusion.

Continuity is the job of the script supervisor, also called the continuity supervisor. They track every detail on set. They note the position of props, the direction of an actor's gaze, the level of a drink, the state of a costume. They take photos and notes. They communicate with the director and the editor. Their work is invisible when it is done well. When it fails, it is the subject of internet lists.

Continuity is not just about avoiding errors. It is about maintaining the logic of the scene. If a character is wounded in one shot, they must show the wound in the next. If a door is locked, it must be unlocked before it opens. The audience may not consciously notice, but they feel it when something is wrong. Continuity keeps the story coherent. It is a technical craft in service of the narrative.