An island // or isle // is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, or a holm. A grouping of geographically or geologically related islands is called an archipelago, e.g. the Philippines.

An island may be described as such despite the presence of an artificial land bridge, for example Singapore and its causeway, or the various Dutch delta islands, such as IJsselmonde. Some places may even retain "island" in their names for historical reasons after being connected to a larger landmass by a wide land bridge, such as Coney Island. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal, it is generally not considered an island.

There are two main types of islands: continental islands and oceanic islands. There are also artificial islands.

The word island comes from Middle English iland, from Old English igland (from ig, similarly meaning 'island' when used independently, and -land carrying its contemporary meaning; cf. Dutch eiland ("island"), German Eiland ("small island")). However, the spelling of the word was modified in the 15th century due to an incorrect association with the etymologically unrelated Old French loanword isle, which itself comes from the Latin word insula.[1] Old English ig is actually a cognate of Latin aqua (water).[2]

Greenland is the world's largest island [3] with an area of over 2.1 million km, while Australia, the world's smallest continent[4] has an area of 7.6 million km, but there is no standard of size which distinguishes islands from continents,[5] or from islets.[6] There is a difference between islands and continents in terms of geology. Continents sit on continental lithosphere which is part of tectonic plates floating high on Earth's molten mantle. Oceanic crust is also part of tectonic plates, but it is denser than continental lithosphere, so it floats low on the mantle. Islands are either extensions of the oceanic crust (e.g. volcanic islands) or geologically they are part of some continent sitting on continental lithosphere(e.g. Greenland).[7] This holds true for Australia, which sits on its own continental lithosphere and tectonic plate.

Continental islands are bodies of land that lie on the continental shelf of a continent. Examples include Borneo, Java, and Sumatra off Asia; New Guinea, Tasmania, and Kangaroo Island off Australia; Great Britain, Ireland, and Sicily off Europe; Greenland, Newfoundland, Long Island, and Sable Island off North America; and Barbados and Trinidad off South America.

A special type of continental island is the microcontinental island, which results when a continent is rifted. Examples are Madagascar and Socotra off Africa, the Kerguelen Islands, New Caledonia, New Zealand, and some of the Seychelles.

Another subtype is an island or bar formed by deposition of tiny rocks where a water current loses some of its carrying capacity. An example is barrier islands, which are accumulations of sand deposited by sea currents on the continental shelves. Another example is islands in river deltas or in large rivers. While some are transitory and may disappear if the volume or speed of the current changes, others are stable and long-lived. Islets are very small islands.

A desert island is an island with no people. Typically, a desert island is denoted as such because it exists in a state of being deserted, or abandoned. An arid desert climate is not typically implied; one dictionary uses the phrase 'desert island' to illustrate the use of 'desert' as an adjective meaning "desolate and sparsely occupied or unoccupied".[8] According to another, "A desert island is a small tropical island, where nobody lives or an undiscovered island."[9]

Oceanic islands are ones that do not sit on continental shelves. The vast majority are volcanic in origin.[10] The few oceanic islands that are not volcanic are tectonic in origin and arise where plate movements have lifted up the deep ocean floor to above the surface. Examples of this include Saint Peter and Paul Rocks in the Atlantic Ocean and Macquarie Island in the Pacific.

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Island - Wikipedia, the free encyclopedia