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.
South Walls
The fact that neither the 2001 or 2011 censuses mention South Walls in their lists of inhabited islands suggests that there is some dubiety about its status as an island. (In 2001 the General Register Office for Scotland defined an island as "a mass of land surrounded by water, separate from the Scottish mainland" and although the inclusion of islands linked man-made constructions is not clear from this definition in practice they list several separately that are joined to one another by bridges and causeways). The evidence for its island status includes: