Very small islands are called islets
A key or cay is another name for a relatively small island.

There are three main types of islands: continental islands, river islands, and volcanic islands. There are also human-made or artificial islands. A grouping of related islands is called an archipelago.

Continental islands are bodies of land that lie upon the continental shelf of a continent. The continental shelf is usually shallower water off the coast of a continent before it drops off deeper. Examples are Greenland and Trinidad.

River islands occur in river deltas and in large rivers.

Volcanic islands are built by volcanoes. Mid-ocean examples are not part of any continent. A well-known example is the Hawaiian Islands (one of the states of the United States).

The largest island in size is Greenland. The island with the most people on it is Java. It is in Indonesia. The second largest island in people is Honshu. It is Japan's largest island in size.