The word 成人 is formed by combining two characters: 成 (chéng), which means "to complete", "to become", or "to grow into", and 人 (rén), which means "person" or "human". Together, they create a conceptual compound that literally signifies "completed person" or "person who has become (full-grown)", directly expressing the idea of an individual who has reached maturity, thus meaning "adult".