An island is a piece of land completely surrounded by water. Islands can be tiny, like a small rock in a lake where turtles sun themselves, or enormous, like Greenland, which spans over 800,000 square miles. Australia is so large that geographers call it a continent rather than an island, even though it's also surrounded by water.

Islands form in different ways. Volcanic islands like Hawaii rise up from the ocean floor when underwater volcanoes erupt and build up layers of hardened lava over millions of years. Other islands are simply hills or mountains that got separated from the mainland when water levels rose, or when rivers carved new channels through the land.

People have lived on islands throughout history, developing unique cultures because of their isolation from mainland societies. Island nations like Japan, Great Britain, and New Zealand became powerful despite (or perhaps because of) being surrounded by water. Islands have also served as refuges, prisons, research stations, and vacation destinations.

The word also appears in common expressions: a kitchen island is a counter that stands alone in the middle of the room, and if you feel like an island, you feel isolated or cut off from others around you.