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.
Estate (land)
More generally and usually in modern times, an estate is any large packet of land in single ownership: seeIn the United States: Long Island, Westchester County, Bar Harbor on Mount Desert Island, and other affluent East Coast enclaves; the San Francisco Bay Area, early Beverly Hills, California, Montecito, California and other affluent West Coast enclaves are estates; all had strong traditions of large agricultural, grazing, and productive estates modeled on those in Europe. However, by the late 1940s and early 1950s, many had been demolished and subdivided, in some cases resulting in suburban villages named for the former owners, as in Baxter Estates, New York.