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.
British Isles
The British Isles are a group of islands in the North Atlantic off the north-western coast of continental Europe that consist of the islands of Great Britain, Ireland, the Isle of Man and over six thousand smaller isles. They have a total area of about 315,159 km and a combined population of just under 70 million, and include two sovereign states, the Republic of Ireland (which covers roughly five-sixths of Ireland) and the United Kingdom of Great Britain and Northern Ireland. The islands of Alderney, Jersey, Guernsey and Sark, and their neighbouring smaller islands, are sometimes also taken to be part of the British Isles, even though, as islands off the coast of France, they do not form part of the archipelago.