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.
Island range
An island range is a mountain range that exists in total or almost total isolation from a larger chain of ranges and sub-ranges. From a distance on the plains, these ranges appear as "islands" of higher ground. They are often described as islands of mountainous land because they exist in the "sea" of lower elevation and flatter prairie country; many examples are found in the northern Rocky Mountains of the United States. Island ranges include the Big Snowy Mountains of east-central Montana, the Crazy Mountains of south-central Montana, or the Wichita Mountains of southwestern Oklahoma. Island ranges, due to their isolation, often have animal and/or plant species or subspecies found nowhere else.