We know the big version: island. But there're others kinds of island. Just look:
Island (a ilha grande) (noun)
a piece of land that is completely surrounded by water
Isle (a ilha poética) (noun) used especially in poetry and names to mean ‘island’: the British Isles.
Islet (ilhota) (noun) a very small island: a rocky islet
Atoll (atol) (noun) an island made of coral and shaped like a ring with a lake of sea water (called a lagoon) in the middle