Why is New Guinea considered the world’s second largest island?

New Guinea is considered the world’s second-largest island based on its total land area, which measures approximately 309,000 to 317,150 square miles (800,000 to 821,400 square km), trailing only Greenland in size.12

Geologically, New Guinea is classified as a continental island. It is an unsubmerged portion of the Australian continental platform, separated from the Australian mainland only by the shallow and narrow Torres Strait. Because it is smaller than a continent and entirely surrounded by water, it meets the technical definition of an island.21