A movie theater (North American English), cinema (British English), or cinema hall (Indian English), also known as a picture house, the pictures, or the movies is a building that contains auditoria for viewing films (also called movies) for entertainment. Most, but not all, theaters are commercial operations catering to the general public, who attend by purchasing a ticket. Some movie theaters, however, are operated by non-profit organizations or societies that charge members a membership fee to view films. The film is projected with a movie projector onto a large projection screen at the front of the auditorium while the dialogue, sounds and music are played through a number of wall-mounted speakers. Since the 1970s, subwoofers have been used for low-pitched sounds. In the 2010s, most movie theaters are equipped for digital cinema projection, removing the need to create and transport a physical film print on a heavy reel. A great variety of films are shown at cinemas, ranging from animated films to blockbusters to documentaries. The smallest movie theaters have a single viewing room with a single screen. In the 2010s, most movie theaters have multiple screens. The largest theater complexes, which are called multiplexes—a design developed in the US in the 1960s—have up to thirty screens. The audience members often sit on padded seats, which in most theaters are set on a sloped floor, with the highest part at the rear of the theater. Movie theaters often sell soft drinks, popcorn, and candy, and some theaters sell hot fast food. In some jurisdictions, movie theaters can be licensed to sell alcoholic drinks. A movie theater may also be referred to as a movie theatre, movie house, film house, film theater or picture house. In the US, theater has long been the preferred spelling, while in the UK, Australia, Canada and elsewhere it is theatre. However, some US theaters opt to use the British spelling in their own names, a practice supported by the National Association of Theatre Owners, while apart from North America most English-speaking countries use the term cinema /ˈsɪnɪmə/, alternatively spelled and pronounced kinema /ˈkɪnɪmə/. The latter terms, as well as their derivative adjectives 'cinematic' and 'kinematic', ultimately derive from Greek κινῆμα, κινήματος (kinema, kinematos)—'movement', 'motion'. In the countries where those terms are used, the word 'theatre' is usually reserved for live performance venues. Colloquial expressions, mostly applied to motion pictures and motion picture theaters collectively, include the silver screen (formerly sometimes sheet) and the big screen (contrasted with the smaller screen of a television set). Specific to North American term is the movies, while specific terms in the UK are the pictures, the flicks and for the facility itself the flea pit (or fleapit). A screening room is a small theater, often a private one, such as for the use of those involved in the production of motion pictures or in a large private residence. The etymology of the term 'movie theater' involves the term 'movie', which is a 'shortened form of moving picture in the cinematographic sense' that was first used in 1896 and 'theater', which originated in the '...late 14c., 'open air place in ancient times for viewing spectacles and plays'. The term 'theater' comes from the Old French word 'theatre', from the 12th century and '...directly from Latin theatrum 'play-house, theater; stage; spectators in a theater'', which in turn came from the Greek word 'theatron', which meant 'theater; the people in the theater; a show, a spectacle', literally 'place for viewing'. The use of the word 'theatre' to mean a 'building where plays are shown' dates from the 1570s in the English language. The earliest precursors to movies were magic lantern shows. Magic lanterns used a glass lens, a shutter and a powerful lamp to project images from glass slides onto a white wall or screen. These slides were originally hand-painted. The invention of the Argand lamp in the 1790s, limelight in the 1820s and the intensely bright electric arc lamp in the 1860s increased the brightness of the images. The magic lantern could project rudimentary moving images, which was achieved by the use of various types of mechanical slides. Typically, two glass slides, one with the stationary part of the picture and the other with the part that was to move, would be placed one on top of the other and projected together, then the moving slide would be hand-operated, either directly or by means of a lever or other mechanism. Chromotrope slides, which produced eye-dazzling displays of continuously cycling abstract geometrical patterns and colors, were operated by means of a small crank and pulley wheel that rotated a glass disc. Still photographs were used later on after the widespread availability of photography technologies after the mid-19th century. Magic lantern shows were often given at fairs or as part of magic shows. A magic lantern show at the 1851 World's Fair caused a sensation among the audience.