In physical geography, a dune is a hill of sand built by either wind or water flow. Dunes occur in different shapes and sizes, formed by interaction with the flow of air or water. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind. The valley or trough between dunes is called a slack. A "dune field" is an area covered by extensive sand dunes.

Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases, the dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated with ancient lake or sea beds.

Dunes can form under the action of water flow (fluvial processes), and on sand or gravel beds of rivers, estuaries and the sea-bed.

The modern word "dune" came into English from French circa 1790.

Dune is a 1984 American epic science fiction film written and directed by David Lynch, based on the 1965 Frank Herbert novel of the same name. The film stars Kyle MacLachlan as young nobleman Paul Atreides, and includes an ensemble of well-known American and European actors in supporting roles. It was filmed at the Churubusco Studios in Mexico City and included a soundtrack by the rock band Toto and Brian Eno. The plot, set twenty one thousand years in the future, concerns the conflict between rival noble families as they battle for control of the planet Arrakis (also known as "Dune"), which is the only planet that possesses the drug melange—also called "the spice"—which is the most essential and valuable commodity in the universe.

After the success of the novel, attempts to adapt Dune as a film began as early as 1971. A lengthy process of development followed throughout the 1970s, during which Arthur P. Jacobs, Alejandro Jodorowsky and Ridley Scott unsuccessfully tried to bring their visions to the screen. In 1981, executive producer Dino De Laurentiis hired Lynch as director.

Arrakis (/əˈrækᵻs/;Arabic: الراقص‎, ar-rāqiṣ, "the dancer") — informally known as Dune and later called Rakis — is a fictional desert planet featured in the Dune series of novels by Frank Herbert. Herbert's first novel in the series, 1965's Dune, is popularly considered one of the greatest science fiction novels of all time, and it is sometimes cited as the best-selling science fiction novel in history.

In Dune, the planet is the home of the Fremen (Zensunni wanderers), and subsequently is the Imperial Capital of the Atreides Empire. Arrakis is the third planet orbiting the star Canopus, and it in turn is orbited by two moons, one of which has the image of the desert kangaroo mouse, Muad'Dib, on it; the other moon possesses the image of a human hand.

Environment and the spice

A desert planet with no natural precipitation, in Dune it is established that Arrakis had been "His Imperial Majesty's Desert Botanical Testing Station" before the discovery of melange, for which it is the only natural source in the universe. Melange (or, "the spice") is the most essential and valuable commodity in the universe, as it extends life and makes safe interstellar travel possible (among other uses). The planet has no surface water bodies, but open canals called qanats are used "for carrying irrigation water under controlled conditions" through the desert. The Fremen collect water in underground reservoirs to fulfill their dream of someday terraforming the planet, and pay the Spacing Guild exorbitant fees in melange to keep the skies over Arrakis free of any satellites which might observe their efforts. As indicated by its large salt flats, Arrakis once had lakes and oceans; Lady Jessica also notes in Dune that wells drilled in the sinks and basins initially produce a "trickle" of water which soon stops, as if "something plugs it."