Piece of land surrounded by water on all sides.

In geography, landforms are natural features of the Earth's surface. They can be classified into various types based on their shape, size, and the way they are formed. One such landform is an island, which is a piece of land that is completely surrounded by water. Islands can be found in oceans, seas, and lakes, and they vary greatly in size, from tiny islets to large landmasses like Madagascar or Greenland.

The term "island" is derived from the Old English word "igland," which means "water-land." Islands are formed through various geological processes, such as volcanic activity, sedimentation, and the rise and fall of sea levels. They can also be formed by the erosion of a larger landmass, such as a peninsula, which is a piece of land that is surrounded by water on three sides but connected to a larger landmass on one side.

In contrast, a plain is a large area of flat land with few trees and a gentle slope. Plains are typically found in the interior of continents and are not surrounded by water on all sides. A plateau, on the other hand, is an area of highland with a relatively flat top and steep sides. Plateaus are also not surrounded by water on all sides.

Understanding the specific definitions and characteristics of these landforms is crucial for identifying and distinguishing them in geographical contexts. In the given question, the description of a piece of land surrounded by water on all sides clearly points to an island, making it the correct answer. This concept is important in various fields, including geography, environmental science, and earth science, and is often tested in competitive examinations such as the UPSC Civil Services, SSC CGL, Bank PO, and State PSC exams.