An archipelago (pronounced /ɑrkəˈpɛləgoʊ/) is a chain or group of islands. The word archipelago means "chief sea", from Greek arkhon (arkhi-) ("leader") and pelagos ("sea").
Types of archipelagos
Archipelagos are usually found in the open sea; less commonly, a big land mass may neighbor them, an example being Scotland which has more than 700 islands surrounding the mainland. Archipelagoes are often volcanic, forming along mid-ocean ridges or hotspots, but there are many other processes involved in their construction, including erosion, deposition, and land elevation.
The four biggest countries that are mainly archipelagos are Japan, the Philippines, the United Kingdom and Indonesia (the world's biggest archipelagic country according to the CIA World Factbook).
The biggest archipelago in the world by size is in Northern Canada, the Canadian Arctic Archipelago, which is in the Arctic Ocean.