A large body of land surrounded by water is called an "island." Islands range in size from less than one acre in area to hundreds of thousands of square miles.
Although continents are also surrounded by water, they are far larger than islands. Islands are found all over the world. The biggest, Greenland, has an area of 836,000 square miles. "Islets" are small ocean islands, while "aits" or "eyots" are islands found in rivers. An "archipelago" is a group of islands in an ocean or sea. Some islands retain their natural state with plants and animals, while others, such as New York City's Manhattan, are completely urbanized.