Expressionism is an artistic movement focused on intense subjectivism and the externalization of personal feelings, often criticizing societal norms. It is characterized by vivid distortions in style and dramatic structure, frequently addressing themes of familial conflict and taboo subjects. Prominent American playwrights like Eugene O'Neill and Sophie Treadwell explored these themes, but the movement declined due to its complex and subjective language becoming less relatable in modern society.