An island or isle is any piece of subcontinental 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. Wikipedia

Island, any area of land smaller than a continent and entirely surrounded by water. Islands may occur in oceans, seas, lakes, or rivers...................................