The term for a landmass that is surrounded by water is an island. Islands can vary greatly in size and type, ranging from small islets to large landmasses like Greenland and Australia. They can be formed through various geological processes, including volcanic activity, sediment accumulation, or rising sea levels. Islands are often home to unique ecosystems and species due to their isolation, making them important sites for biodiversity. They can also hold cultural and historical significance, serving as settlements, tourist destinations, or strategic military locations throughout history.