An island is a fairly small piece of land and a continent is a great big piece of land. The island of Australia is big enough to be called a continent, for it is about as big as the United States. The island of Greenland is only about one quarter of this size   which is why it is not big enough to be called a continent.

On certain maps, Greenland looks much larger than this, much larger than it really is. This is because these maps show the face of the earth as a flat area, when actually it curves around the globe. The surface of the earth tapers from the wide equator towards the poles and Greenland is not far from the north pole. To get this tapering area onto a flat map, it must be stretched out wide, which is why Greenland looks bigger than it actually is. In any case, it is the largest island in the world.