Geography glossary

Terms A – E

Continent

A continent is a large, continuous landmass on Earth. The Earth has seven continents: Asia, Africa, Europe, North America, South America, Oceania and Antarctica. Sometimes North and South America are counted as one continent, or Europe and Asia are combined as Eurasia — it depends on which definition you use.

Landmass

A landmass is a large, continuous area of land. The term is often used to describe a continent or a large island. Unlike a continent, a landmass does not necessarily imply a distinct geological or cultural identity — it is a purely geographical description. Each continent is a landmass, but not every landmass is a continent.

Ocean

An ocean is a vast, continuous body of salt water that surrounds the continents. There are officially five oceans: the Pacific Ocean (the largest, at 168.7 M km²), the Atlantic Ocean (85.1 M km²), the Indian Ocean (70.6 M km²), the Southern Ocean and the Arctic Ocean. Source: NOAA / IHO.

Equator

The equator is an imaginary line that divides the Earth into two equal halves: the northern and southern hemispheres. The equator lies at latitude 0° and passes through countries including Kenya, Indonesia, Ecuador and Brazil. On the equator, day and night are almost equal in length throughout the year (each roughly twelve hours).

Island

An island is a piece of land surrounded by water on all sides. Islands can be tiny — a rocky outcrop in the sea — or enormous. Greenland is the largest island in the world (2,200,000 km²). Australia is not usually considered an island but a continent, even though it is entirely surrounded by water. The continent of Oceania consists of thousands of islands.

Terms H – K

Hemisphere

The Earth is divided into two halves called hemispheres. The northern hemisphere covers everything above the equator (including Europe, North America and most of Asia). The southern hemisphere covers everything below the equator (including Antarctica, Australia, the southern part of Africa and South America). The hemispheres have opposite seasons: when it is summer in Britain, it is winter in Australia.

Tropic

The tropics are two imaginary circles around the Earth at 23.5° latitude north (Tropic of Cancer) and south (Tropic of Capricorn) of the equator. Between the two tropics lies the tropical zone: a band around the Earth that is warm all year round. Here the sun is directly overhead at certain times of year — unique to this zone.

Arctic / Antarctic Circle

The Arctic Circle is an imaginary line at 66.5° N latitude; the Antarctic Circle is at 66.5° S. Above the Arctic Circle and below the Antarctic Circle you get the midnight sun in summer: the sun does not set. In winter the reverse is true — complete darkness all day. Parts of Norway, Finland and Iceland lie above the Arctic Circle.

Latitude

Lines of latitude are imaginary horizontal lines running around the Earth parallel to the equator. They show how far north or south of the equator you are, measured in degrees (0° to 90°). The equator is 0°; the North Pole is 90° N. The United Kingdom lies at roughly 50°–60° N.

Climate

Climate is the average weather at a place over a long period, usually thirty years. Climate differs from weather: weather is what you experience today, climate is the pattern. The Earth has several climate zones: tropical, subtropical, temperate, polar and desert. Climate depends on latitude, altitude above sea level, proximity to the ocean and prevailing winds. More about climate classification under the entry for Köppen.

Köppen

The Köppen-Geiger climate classification is a widely used system for categorising climates. It was devised by German-Russian climatologist Wladimir Köppen (1846–1940) and later revised by Rudolf Geiger. The system uses letters: A = tropical, B = dry, C = temperate, D = cold/continental, E = polar. The United Kingdom has a Cfb climate (temperate, no dry season, warm summer). Source: Köppen-Geiger classification.

Terms L – M

Longitude

Lines of longitude are imaginary vertical lines on the globe running from the North Pole to the South Pole. They show how far east or west of the prime meridian you are. The prime meridian (0°) runs through Greenwich, London. Longitude runs from 0° to 180° east and 180° west. Together with latitude, longitude forms a coordinate system that can pinpoint any location on Earth.

Meridian

A meridian is another name for a line of longitude. The Prime Meridian, also called the Greenwich Meridian, is the international zero point for longitude and the basis for time zone boundaries. The International Date Line runs roughly along the 180° meridian, on the opposite side of the Earth.

Terms R – T

Rainforest

A rainforest is a dense tropical or subtropical forest with very high rainfall — at least 2,000 mm per year. Rainforests are found mainly around the equator: the Amazon rainforest in South America is the largest in the world. Rainforests contain more than half of all known animal and plant species on Earth. Deforestation is destroying them rapidly, posing a major threat to climate and biodiversity.

Savanna

A savanna is an open landscape of grasses, shrubs and scattered trees in the tropics or subtropics. The savanna has a dry and a wet season. Vast savanna belts cross Africa, providing habitat for elephants, lions, zebras and giraffes. Savanna climates fall into the A and B classes of the Köppen system.

Taiga

The taiga (also: boreal forest or coniferous forest) is the largest forest type on Earth. It stretches across northern Canada, Scandinavia and Russia. The taiga consists mainly of spruce, pine and larch trees that can withstand long, harsh winters. In Siberia the taiga is so vast that it has its own climate and water cycle.

Time zone

A time zone is a region of the Earth that uses the same official time. The Earth is divided into 24 main time zones, each covering 15° of longitude (the Earth rotates 360° in 24 hours, so 360°÷24=15° per hour). In practice, boundaries deviate because of national borders and political decisions: China uses a single time zone for the whole country, whereas geographically it would span five. More details on the time zones page.

Tundra

The tundra is a treeless region in the polar zones where summers are short and cold and trees cannot grow. The soil thaws only a few centimetres in summer; below that it stays frozen (permafrost). Lichens, grasses and dwarf shrubs are the typical vegetation. Reindeer, lemmings, arctic wolves and migratory birds (in summer) inhabit the tundra. Tundra landscapes are found in the Arctic and along the coastal fringe of Antarctica.

Terms U – W

UTC

UTC stands for Coordinated Universal Time. It is the worldwide time standard against which all time zones are measured. UTC+0 is the time in Greenwich, London in winter. The UK uses UTC+0 in winter and UTC+1 in summer (BST). Before 1972 this standard was called GMT (Greenwich Mean Time); in practice UTC and GMT are still often used as synonyms. Source: IANA time zone database.

Desert

A desert is a region that receives less than 250 mm of rainfall per year. Deserts are not always hot: the Sahara is a hot desert, but Antarctica is the world's largest cold desert. The Sahara in Africa is the largest hot desert (roughly 9,000,000 km²). In dry desert regions, specialised plants and animals that need little water survive, including camels, cacti and reptiles.

Population density

Population density is the average number of inhabitants per square kilometre. You calculate it by dividing the population by the area: population ÷ area (km²) = density (inhabitants/km²). Bangladesh has an extremely high density of roughly 1,100 inhabitants/km²; Mongolia has one of the lowest in the world with just 2 inhabitants/km². Compare continents on the compare page. Source: UN WPP 2024.

Capital city

The capital city is the city where a country's national government is based. The capital is not always the largest city: Australia's capital is Canberra, but Sydney is far larger. In Asia, Tokyo is both the capital and the largest city of Japan. Official capitals by country are listed in the CIA World Factbook.