A peninsula is a piece of land that extends from a mainland and is surrounded by water on most, but not all of its borders. It is also sometimes defined as a piece of land bordered by water on three of its sides. The word "peninsula" comes from the Latin words "paene" (almost) and "insula" (island) because a peninsula is almost an island, but not quite.

Some key characteristics of a peninsula include:

• It is a landform that extends from a mainland into a body of water.
• It is surrounded by water on most, but not all, of its borders.
• It is connected to the mainland on one side.

Examples of peninsulas include Florida in the United States, the Iberian Peninsula in Europe, and the Korean Peninsula in Asia.