Asia is the world's largest and most populous continent. It covers 8.6% of the Earth's total surface area (or 29.9% of its land area) and, with over 4 billion people, it contains more than 60% of the world's current human population. Chiefly in the eastern and northern hemispheres, Asia is traditionally defined as part of the landmass of Eurasia - with the western portion of the latter occupied by Europe - lying east of the Suez Canal, east of the Ural Mountains, and south of the Caucasus Mountains and the Caspian and Black Seas. It is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, and on the north by the Arctic Ocean.
Africa is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km - (11.7 million sq mi) including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With about 922 million people (as of 2005) in 61 territories, it accounts for about 14.2% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Suez Canal and the Red Sea to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. There are 53 countries, including Madagascar and various island groups, associated with the continent.
North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the south and west by the North Pacific Ocean; South America lies to the southeast. North America covers an area of about 24,709,000 square kilometers (9,540,000 square miles), about 4.8% of the planet's surface or about 16.5% of its land area.
South America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean; North America and the Caribbean Sea lie to the northwest.
Europe is, conventionally, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, and by the Caucasus Mountains to the southeast. Europe is washed upon to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Sea, and to the southeast by the Black Sea and the waterways connecting it to the Mediterranean. Yet, the borders for Europe - a concept dating back to classical antiquity - are somewhat arbitrary, as the term continent can refer to a cultural and political distinction or a physiographic one.
Oceania (sometimes Oceanica) is a geographical, often geopolitical, region consisting of numerous lands—mostly islands in the Pacific Ocean and vicinity. The term "Oceania" was coined in 1831 by French explorer Dumont d'Urville. The term is used today in many languages to define one of the continents and is one of eight terrestrial ecozones.