continents

Greenland is the largest island on Earth at about 2.16 million square kilometres — but Australia, which is more than three times bigger, isn't on the list at all. The reason isn't size; it's a definition. Australia is classified as a continent, and the moment a landmass becomes a continent, it stops being an island. That single rule explains the entire ranking, and a famous map projection explains why Greenland looks even bigger than it is.

An Earth covered entirely by ocean — a 'water world' — would have no terrestrial life, simpler climate dynamics, and a chemistry profoundly altered by the absence of continental weathering. Land has shaped Earth far more than most people realize.