Region is a concept that is used to identify and organize areas of Earth’s surface for various purposes. A region has certain characteristics that give it a measure of cohesiveness and distinctiveness that set it apart from other regions. As worlds within worlds, regions can be used to simplify the whole by organizing Earth’s surface on the basis of the presence or absence of selected physical and human characteristics. As a result, regions are human constructs whose boundaries and characteristics are derived from sets of specific criteria. They can vary in scale from local to global; overlap or be mutually exclusive; exhaustively partition the entire world or capture only selected portions of it. They can nest within one another, forming a multilevel mosaic. Understanding the idea of region and the process of regionalization is fundamental to being geographically informed.

Understanding the nature of regions requires a flexible approach to the world. The criteria used to define and delimit regions can be spatially precise as coastlines and political boundaries or as spatially amorphous as suggesting the general location of people with allegiances to a particular professional athletic team or identifying a market area for distributing the recordings of a specific genre of music. Regions can be as small as a neighborhood or as vast as a territorial expanse covering thousands of square miles in which the inhabitants speak the same language. They can be areas joining people in common causes where they can become areas for conflict, both internal and external. Geographers define regions in three basic ways:

The first type is the formal region. It is characterized by a common human property, such as the presence of people who share a particular language, religion, nationality, political identity or culture, or by a common physical property, such as the presence of a particular type of climate, landform, or vegetation. Political entities such as counties, states, countries, and provinces are formal regions because they are defined by a common political identity. Other formal regions include climate regions (e.g., areas with a Mediterranean climate), landform regions (e.g., the Ridge and Valley and Piedmont regions of Pennsylvania), and economic regions (e.g., the wheat belt of Kansas, the citrus-growing areas of south Texas, and the irrigated farmlands of the Central Valley of California). Formal regions can be defined by measures of population, per capita income, ethnic background, crop production, population density and distribution, or industrial production, or by mapping physical characteristics such as temperature, rainfall, growing season, and average date of first and last frost.

The second type of region is the functional region. It is organized around a node or focal point with the surrounding areas linked to that node by transportation systems, communication systems, or other economic association involving such activities as manufacturing and retail trading. A typical functional region is a metropolitan area (MA) as defined by the Bureau of Census. For example, the New York MA is a functional region that covers parts of several states. It is linked by commuting patterns, trade flows, television and radio broadcasts, newspapers, travel for recreation and entertainment. Other functional regions include shopping regions centered on malls or supermarkets, area served by branch banks, and ports and their hinterlands.

The third type of region is the perceptual region. It is a construct that reflects human feelings and attitudes about areas and is therefore defined by people’s shared subjective images of those areas. It tends to reflect the element of people’s mental maps, and, although it may help to impose a personal sense of order and structure on the world, it often does so on the basis of stereotypes that may be inappropriate or incorrect. Thus southern California, Dixie, and the upper Midwest are perceptual regions that are thought of as being spatial units, although they do not have precise borders or even commonly accepted regional characteristics and names.

Some regions, especially formal regions, tend to be stable in spatial definition, but may undergo change in character. Others, especially functional regions, may retain certain basic characteristics, but may undergo spatial redefinition over time. Yet other regions, particularly perceptual regions, are likely to vary over time in both spatial extent and character.

Regional change, in the context of the human spatial organization of Earth’s surface, is an area of study that provides students with opportunities to examine and learn about the complex web of demographic and economic changes that occur.

Regions serve as a valuable organizing technique for framing detailed knowledge of the world and for asking geographic questions. Because regions are examples of geographic generalizations, students can learn about the characteristics of other regions of the world by knowing about one region. Knowing about the physical processes that create the Mediterranean climate and vegetation of southern California, for example, can serve as an analogue for learning about other regions with Mediterranean climates and vegetation in Australia, Europe, South America, and Africa. Regions provide a context for discussing similarities and differences between parts of the world.

Through understanding the idea of region, students can apply geographic knowledge, skills, and perspectives to solving problems as immediate as making an informed decision about a neighborhood zoning issue or as long-range as predicting the reconfiguration of political and economic alliances owing to resource shortages or changes in the global ecosystem. Most importantly, studying regions enables students to synthesize their understanding of the physical and human properties of Earth’s surface at scales that range from local to global.