Otok je dio kopna manji od kontinenta a veći od hridi (stijene, rta, grebena). Može se nalaziti u rijeci (gdje se naziva i ada), jezeru ili moru.

An island or isle is any piece of land that is completely surrounded by water. Very small islands such as emergent land features on atolls are called islets. A key or cay is another name for a small island or islet . An island in a river or lake may be called an eyot, IPA [aɪət]. There are two main types of islands: continental islands and oceanic islands. There are also artificial islands. A grouping of geographically and/or geologically related islands is called an archipelago.