Short film, feature, TV episode, commercial

The length of a work and what its audience expects decide the shape of the story. A short film has room for one situation and one turn, and lives on its ending; a feature needs a goal strong enough for 90 minutes, a commitment, a low point and a midpoint that breaks up the second act.

A TV episode braids A, B and C stories inside the rules of the series bible and still builds to act breaks; a pilot works more like a feature. A commercial has time for one idea and one feeling, with the product inside the turn and every claim verifiable.