An island is a body of land that is isolated (not connected to another body of land) and is currently surrounded by water around its entire coastline. Examples of islands include Hawaii (U.S. state), Saint Maarten, and the Canary Islands. A chain of islands that are geographcally related is called an archipelago, and small islands which generally do not support life are islets.
Most islands are created by volcanic eruption or by tectonic activity, but one island on record has been created by man-made means: Kansai International Airport (KIX) in Japan is the world's first ocean airport built entirely on a landfill island in Osaka Bay.
A less common use of the word 'island' relates to isolated populations of species. From the point of view of aquatic life, for instance, a lake is an 'island' while the surrounding land is inhabitable, just as the sea is inhospitable to human life confined to land islands. Likewise, mountain peaks that support life which cannot survive in lower, drier altitudes are effectively 'islands', since their species are cut off from each other by the lower terrain that cannot support them. Such isolation often leads to theevolution of new species; for example, 'Darwin's finches' are several species of passerine birds which originally evolved from a common ancestor on different islands of the Galápagos.