Genre theory seeks to recognize film as both an artistic and commercial medium. It developed as an alternative to auteur theory, which viewed directors as the sole authors of films. Genres are both defined by critics and exist independently, as studios try to replicate successful film types. However, defining genres is complicated, as films can fit multiple categories and subgenres exist. The meaning and conventions of genres also depend on historical and cultural context. Overall, genre theory examines patterns of similarity and difference between films.