An island is a piece of land that is completely surrounded by water. Islands can vary in size, from small landmasses that can be walked around in a few minutes to large areas that can support entire communities. They can be found in oceans, seas, rivers, and lakes. Islands are formed through various geological processes, such as volcanic activity or the accumulation of sand and coral. Some well-known islands include Hawaii, Bali, and Madagascar. Islands can host unique ecosystems and wildlife, often leading to a rich diversity of plants and animals that may not be found elsewhere.