How life develops on islands. Islands lie in oceans, rivers, and lakes throughout the world. They vary greatly in size. Greenland is the largest island in the world.
Some islands cover a smaller area than a city block.
A small island is called an islet. The distinction between a continent and an island is based on size. Australia is more than three times as large as Greenland. Because of its size, geographers class it as a continent. Islands make up the entire land area of some countries, including Japan and the Philippines.