A continent is one of several very large landmasses on Earth. Generally identified by convention rather than any strict criteria, up to seven regions are commonly regarded as continents. Ordered from largest in size to smallest, they are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. In geology, areas of continental crust include regions covered with water.
Islands are frequently grouped with a neighbouring continent to divide all the world's land into geopolitical regions. Under this scheme, most of the island countries and territories in the Pacific Ocean are grouped together with the continent of Australia to form a geopolitical region called Oceania.
By convention, "continents are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water." Many of the seven most commonly recognized continents identified by convention are not discrete landmasses separated completely by water. The criterion "large" leads to arbitrary classification: Greenland, with a surface area of 2,166,086 square kilometres (836,330 sq mi) is considered the world's largest island, while Australia, at 7,617,930 square kilometres (2,941,300 sq mi) is deemed the smallest continent.
The Earth's major landmasses all have coasts on a single, continuous world ocean, which is divided into a number of principal oceanic components by the continents and various geographic criteria.
The most restricted meaning of continent is that of a continuous area of land or mainland, with the coastline and any land boundaries forming the edge of the continent. In this sense the term continental Europe (sometimes referred to in Britain as "the Continent") is used to refer to mainland Europe, excluding islands such as Great Britain, Ireland, Malta and Iceland, and the term continent of Australia may refer to the mainland of Australia, excluding Tasmania and New Guinea. Similarly, the continental United States refers to the 48 contiguous states in central North America and may include Alaska in the northwest of the continent (the two being separated by Canada), while excluding Hawaii in the middle of the Pacific Ocean.