An atoll is a ring-shaped coral reef, island, or series of islets. The term 'atoll part' refers to the individual components that make up an atoll. An island is a large landmass surrounded by water and is typically larger than an ISLET. An ISLET is a small island, usually no more than a few hundred meters in diameter. An ISLE is a smaller version of an island, typically less than 10 kilometers in diameter.