The word is derived from the Greek words geo ("the Earth") and graphein ("to write").

The surface of the Earth is the interface of the atmosphere, lithosphere, hydrosphere, and biosphere. It provides the habitat, or environment, in which humans are able to live. This habitable zone has a number of special characteristics. One of the most important is the complex interaction among many physical, biologic, and human elements of the Earth, such as land surface, climate, water, soil, vegetation, agriculture, and urbanization. Another characteristic is the high variability of the environment from place to place--hot tropics to cold polar regions, dry deserts to humid equatorial forests, vast level plains to rugged mountains, and uninhabited ice caps to densely settled metropolitan areas. Yet another is the consistency with which significant patterns occur, which makes possible generalizations about distributions; obvious examples are measurements of temperature and rainfall, which are the most important climatic elements affecting farming and many other human activities.

Geographic study is particularly concerned with location, with areal patterns, with the interrelationships of phenomena (especially of the relationship between human society and the land, as in ecology), with rationalization, and with ties among areas. Typical areas of inquiry include where people live; in what sort of patterns they are distributed over the Earth's surface; what factors of environment, resources, culture, and economic development account for this distribution; whether or not significant regions can be recognized by types of population, livelihood, and culture; and what types of movements and relations occur among places.

Cultural and social geography

Five major themes characterize cultural geography: culture, culture area, cultural landscape, cultural history, and cultural ecology. The cultural geographer studies the distribution in space and time of cultures and the elements of culture, such as artifacts and tools, techniques, attitudes, customs, languages, and religious beliefs; cultural complexes in their spatial organization; the cultural landscape--i.e., the association of human, biologic, and physical features on the surface of the Earth (especially as perceived visually), ranging from the natural landscape unaffected by humankind to the landscape as thoroughly transformed by human action; the evolution and succession of cultures and cultural elements, including the history of cultural origins and their areal diffusion; and the complex interrelationships and areal associations of culture and nature. The American geographer Carl O. Sauer was particularly creative in working the concepts and teaching of anthropology, archaeology, and sociology into geography.

Whereas the focus of cultural geography is more on traditional societies (though it is not restricted to them), social geography is more oriented toward urban problems in countries with advanced economies. Social geographers have been concerned particularly with the spatial aspects of disadvantaged groups (such as minorities, women, the aged, and the poor), of such social pathologies as crime and mental illness, and of inequality, social welfare, and housing.

Urban geography

Urban geography generally takes a much broader scope than cultural geography; it is a major field in the countries with well-developed economies and high levels of urbanization--western Europe, North America, Australia, and Japan. Among topics investigated are factors affecting the location of individual cities, urban systems as networks of settlement points, regional differences in urbanization, cities in relation to their tributary areas or spheres of influence, the hierarchy of central places, the characteristics of city-size regularities (such as the rule of ranking cities according to size), functional types of cities (economic classification), expansion of metropolitan areas, internal spatial structure of land use, urban transportation and areal patterns of commuting, social problems in cities, housing, and cities as growth poles. One of the seminal contributions to the discipline was made by the German geographer Walter Christaller, who in the first half of the 20th century studied the urban centers of southern Germany and demonstrated that there existed a hierarchy among these centers as well as spacing and size regularities in tributary areas.

Cities are often the locus of studies for many branches of geography--economic, social, or political. The relative role of urban geography has increased dramatically during the 20th century, as the proportion of the population living in urban areas has risen and as interest in the field of geography has shifted from the concern with agricultural geography (and its emphasis on physical factors, such as rainfall, temperature, and soil) to a focus on the burgeoning urban agglomerations as centers of economic, political, and social development and problems. Symbolic of this shift have been studies undertaken of the function of cities as office centers, in which offices are concentrated in skyscrapers that are packed together in central business districts for maximum accessibility to financial, legal, and marketing services both inside and outside the city. Although the development of high-speed express highways and of regional airports has tended to diffuse activities within metropolitan areas from central cities to suburban fringes--housing, manufacturing, and retail trade in particular have exhibited this tendency--the growth of business service activities and of office functions has tended to maintain high daytime populations in central areas, with workers often commuting from suburban communities and metropolitan fringes.