Island
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, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines.
Lake island
Artificial or man-made islands are islands constructed by human activity rather than formed by natural means. They may be totally created by humans, enlarged from existing islands or reefs, formed by joining small existing islands, or cut from a mainland (for example, by cutting through the isthmus of a peninsula). Artificial islands have a long history, dating back to the crannogs of prehistoric Britain and Ireland, and the traditional floating Uru islands of Lake Titicaca in South America. Notable early artificial islands include the Aztec city of Tenochtitlan, at the site of modern Mexico City. Though technically caused by human activity, islands formed from hilltops by the deliberate flooding of valleys (such as in the creation of hydroelectricity projects and reservoirs) are not normally regarded as artificial islands.