Films can be shown on television. Camera zooms in on the screen. We have seen documentaries, comedies, dramas, and horror films. Some are adaptations of books, other were created to be films from the start. The problem in defining films lies within the vast differences in film narrative, genre, and production.
Films have directors but so do television programs.
Not all films are shown in theaters, some go directly to videotape. Therefore, let us say that films are best defined by what the intentions of the creators are. In other words, since we cannot tangibly define films by what they are let us say that if an individual sets out to make a film, independent or studio driven, funny or sad, in a theater on a TV, or on a computer screen, then it is by our definition, a film.