An archipelago is a group or chain of islands clustered together in a body of water. The word comes from Greek roots meaning “chief sea,” since these island groups dot the ocean like scattered puzzle pieces.

Japan is a famous archipelago with four main islands and thousands of smaller ones stretching across the Pacific Ocean. The Hawaiian Islands form another archipelago, created by underwater volcanoes that built up over millions of years until they rose above the waves. Indonesia contains the world's largest archipelago, with over 17,000 islands spread across Southeast Asia.

Archipelagos form in different ways. Some, like Hawaii, emerge from volcanic activity on the ocean floor. Others, like the Florida Keys, are made of coral and limestone. Still others were once connected to continents but became separated when sea levels rose after the last Ice Age.

People who live in archipelagos often become skilled sailors and boat builders, since water travel connects their communities. The Philippines, Greece, and the Caribbean are all places with archipelagos where boats have served as an important form of transportation for thousands of years. Living on an archipelago means your neighbors might be across the water rather than down the street, and getting to school or visiting friends might require a ferry ride instead of a car trip.