A short film is a film with a low running time. The Academy of Motion Picture Arts and Sciences (AMPAS) defines a short film as "an original motion picture that has a running time of not more than 40 minutes including all credits". Other film organizations may use different definitions, however; the Academy of Canadian Cinema and Television, for example, currently defines a short film as 45 minutes or less in the case of documentaries, and 59 minutes or less in the case of scripted narrative films.
In the United States, short films were generally termed short subjects from the 1920s into the 1970s when confined to two 35 mm reels or less, and featurettes for a film of three or four reels. "Short" was an abbreviation for either term.