An island is a piece of land surrounded by water on all sides. Islands can be found in oceans, seas, lakes, and rivers.
How islands form
Islands can form from volcanoes, coral reefs, rising sea levels, erosion, river deposits, or pieces of land separated from larger landmasses.
Island versus peninsula
A peninsula is almost surrounded by water but remains connected to a larger landmass. An island is fully surrounded by water.
Islands can be tiny or huge, but they are not classified as continents.