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A short film is any film not long enough to be considered a feature film. No consensus exists as to where that boundary is drawn: the Academy of Motion Picture Arts and Sciences defines a short film as "an original motion picture that has a running time of 40 minutes or less, including all credits". The term featurette originally applied to a film longer than a short subject, but shorter than a standard feature film.
The increasingly rare term short subject means approximately the same thing. An industry term, it carries more of an assumption that the film is shown as part of a presentation along with a feature film. Short is an abbreviation for either term. Short films can be professional or amateur productions. Short films are often screened at local, national, or international film festivals. Short films are often made by independent filmmakers for non profit, either with a low budget, no budget at all, and in rare cases big budgets. Short films are usually funded by film grants, non profit organizations, sponsor, or out of pocket funds. These films are used by indie filmmakers to prove their talent in order to gain funding for future films from private investors, entertainment companies, or film studios. Short films do qualify for Academy Awards if screened in Los Angeles.
Longer and shorter films coexisted with similar popularity throughout the early days of film. However, comedy short films were produced in large numbers compared to lengthy features such as D.W. Griffith's, "Birth of Nation" . By the 1920s, a ticket purchased a varied program including a feature and several supporting works from categories such as second feature, short comedy, 5–10 minute cartoon, and newsreel.
Short comedies were especially popular, and typically came in a serial or series (such as the Our Gang movies, or the many outings of Charlie Chaplin's Little Tramp character). Even though there was often no set release schedule, these series could be considered somewhat like a modern TV sitcom – lower in status than feature films but nevertheless very popular (comedians such as Laurel and Hardy, Charlie Chaplin and Buster Keaton all 'graduated' from shorts to features).
Animated cartoons came principally as short subjects, as did newsreels. Virtually all major film production companies had units assigned to develop and produce shorts, and many companies, especially in the silent and very early sound era, produced mostly or only short subjects.
In the 1930s, the distribution system changed in many countries owing to the Great Depression. Instead of the cinema owner assembling a program of their own choice, the studios sold a package centered on a main and supporting feature, a cartoon and little else. With the rise of the double feature as a cinema programming format, 2-reel shorts went into decline as a commercial category. Hal Roach, for example, moved Laurel and Hardy full-time into feature films after 1935, and halved his popular Our Gang films to one reel. By the 1940s, he'd moved out of short films altogether (though MGM continued the Our Gang shorts until 1944).
Later shorts include George O'Hanlon's Joe McDoakes movies, and the animated work of studios such as Walt Disney Productions, Leon Schlesinger Productions/Warner Bros. Cartoons, Walter Lantz and Fleischer / Famous Studios. By the mid-1950s, with the rise of television, the commercial live-action short was virtually dead, The Three Stooges being the last major series of 2-reelers, ending in 1959. Short films had become a medium for student, independent and specialty work.
Cartoon shorts had a longer life, due in part to the implementation of lower-cost limited animation techniques, but also declined in this period. Warner Bros., one of the most prolific of the golden era, shut down its studio permanently in 1969. Woody Woodpecker was the last of the "golden era" cartoons to end, shutting down in 1972. The Pink Panther was the last regular theatrical cartoon short series, having begun in 1964 (and thus having spent its entire existence in the limited animation era) and ended in 1980. By the 1960s, the market for animated shorts had largely shifted to television, and even the existing theatrical shorts were being secondarily syndicated to television stations.
Modern era 
A few animated shorts continue within mainstream commercial distribution. For instance, Pixar has screened a short along each of its feature films during its initial theatrical run since 1995 (producing shorts permanently since 2001). Since Disney acquired Pixar in 2005, Disney has also produced animated shorts since 2007 with the Goofy short How to Hook Up Your Home Theater and produced a series of live action ones featuring The Muppets for viewing on YouTube as viral videos to promote the 2011 movie of the same name.
Dreamworks Animation often produces a short sequel to include in the special edition video releases of major features, and are typically of a sufficient length to be broadcast as a TV special. Warner Brothers often includes old animated shorts from its considerable library, connected only thematically, on the DVD releases of classic WB movies.
Shorts are occasionally broadcast as filler when a feature film or other work doesn't fit the standard broadcast schedule. ShortsTV was the first television channel dedicated to short films.
However, short films generally rely on festival exhibition to reach an audience. Such movies can also be distributed via the Internet. Certain websites which encourage the submission of user-created short films, such as YouTube and Vimeo have attracted large communities of artists and viewers. Sites like FILMSshort and the BBC Film Network focus on showcasing curated shorts.
Short films are a typical first stage for new professional filmmakers. But professional actors and crews still choose to create short films as alternative form of expression. Short film making is growing in popularity as equipment becomes cheaper and more amateurs are making movies. "Prosumer" or semi-professional cameras now cost under USD$3,000, and free or low-cost software is widely available that is capable of video editing, post-production work and DVD authoring.
Tropfest is the world's largest short film festival and is generally regarded as one of the most prestigious. Tropfests now take place in Australia (its birthplace), Arabia, the US and elsewhere. Originating in 1993, Tropfest is often credited as being at least partially responsible for the recent popularity of short films internationally.
Short shorts 
Short short films are sometimes considered to be a category of their own. The International Festival of Very Shorts is a festival based in Paris, which shows only movies less than three minutes long. Filminute, the international one-minute film festival, has presented and promoted a collection of one-minute films across multiple media since September 2006. They are known for their conciseness and entertainment value.
See also 
- Reel#Motion picture terminology for an explanation of the historic term "two-reeler"
- List of animated short series
- List of independent short films
- List of short live-action films
- List of short subjects by Hollywood studio
- Movieola: The Short Film Channel
- The Journal of Short Film
- Short Film Granary - professional and amateur short films from around the world
- Short Films at the Open Directory Project
- British Film Institute: "Writing Short Films" by Phil Parker screenonline, website of the British Film Institute