APHG all units

Absolute location

The exact position of a place on the Earth’s surface, expressed in coordinates (latitude and longitude). It remains fixed over time.

Relative location

The position of a place compared to other locations, often described by surroundings or distance. For example, “northwest of City X.”

Site

The physical and human characteristics of a place itself (e.g., climate, terrain, resources). A site is an absolute location at the local level.

Situation

The geographic context of a place, defined by its connections and accessibility to other places (e.g., transport links). Situation is a type of relative location.

Toponym (place name)

The name given to a place on Earth, often reflecting geographic, historical, or cultural significance.

Scale

The ratio or relationship between distance on a map and actual distance on the ground. Can also refer to the level of analysis (local, regional, global). A larger scale map shows a smaller area in more detail.

Region (formal/uniform)

An area defined by officially recognized, uniform characteristics (such as language or climate) that are relatively constant throughout.

Functional (nodal) region

An area organized around a focal point or node (such as a city and its commuter zone), where the characteristic is strongest at the center and diminishes outward (e.g., a metropolitan area).

Perceptual (vernacular) region

A region defined by people’s beliefs or feelings about its identity and characteristics (e.g., “the South” in the U.S.), not by official boundaries.

Place

The unique physical and human attributes that give a location meaning and character (e.g., landmarks, cultural features). Also expressed as sense of place, how attached people are to a location.

Space (spatial)

The physical gap or interval between two or more objects or locations. Spatial concepts include how and why things are arranged in space and related to each other.

Absolute distance

The measurable physical distance between two places (often in miles or kilometers).

Relative distance

A measure of distance that considers cultural or environmental factors (e.g., “a 2-hour drive”). It can change over time with new technology or infrastructure.

Scale of analysis

The level (from local to global) at which a geographic problem or phenomenon is examined. Geographic patterns can look different at different scales.

Space-time compression

The reduction in time it takes for something to reach another place, due to improved transportation or communication (e.g., faster travel shrinking perceived distance).

Connectivity

The directness and strength of linkages between places (e.g., roads, flights, internet); high connectivity means easy flow of people, goods, or ideas.

Accessibility

The ease of reaching destinations from a given location (often influenced by connectivity and distance). Places with high accessibility attract more interaction.

Spatial interaction

The movement of people, goods, or ideas within and between areas. It depends on distance, connectivity, and distance decay (interaction decreases with distance).

Distance decay

The principle that interaction between two places declines as the distance between them increases. In other words, closer places interact more.

Friction of distance

Similar to distance decay; it refers to the hindering effects of distance (time, cost) on movement or communication.

Network

A chain of communication or transportation that connects places (e.g., highways, airline routes, internet).

Diffusion

The process by which a characteristic (such as an innovation, idea, or cultural trait) spreads across space from one place to another.

Relocation diffusion

Spread of a feature or trait by people moving from one place to another (e.g., migrants bringing their culture).

Expansion diffusion

Spread of a feature through a snowballing effect from a central hearth across adjacent areas. It includes

Hierarchical diffusion

Spread from larger or more powerful places to smaller or less powerful ones (e.g., fashion trends from major cities to rural areas)

Contagious diffusion

Rapid, widespread diffusion of a characteristic throughout the population (e.g., viral internet meme).

Stimulus diffusion

Spread of an underlying principle, even if the specific trait itself does not spread (e.g., McDonald’s menus adapting to local tastes).

Cultural landscape

The visible imprint of human activity on the landscape (e.g., buildings, roads, signage). It reflects cultural values, economic activities, and social structures.

Built environment

The physical artifacts and infrastructure that humans create (buildings, parks, roads) as part of the cultural landscape.

Sequent occupance

The notion that successive societies leave their cultural imprints on a landscape (layering), shaping its evolution over time.

Possibilism

The theory that physical environment sets limits on human actions, but culture is determined by social conditions. It counters the older idea of environmental determinism.

Environmental determinism

An outdated theory that the physical environment (climate, terrain) solely shapes human cultures and societies (largely rejected in modern geography).

Region (see above) and pattern

Pattern refers to the geometric arrangement of objects in space (e.g., linear, clustered, dispersed) and is a basic geographic concept.

Distribution

The arrangement of a feature in space. Geographers examine distribution in terms of concentration, density, and pattern.

Arithmetic density

The total number of people divided by total land area; a general measure of population density.

Physiological density

The number of people per unit area of arable (farmable) land; indicates pressure on productive land.

Grid

The system of imaginary lines of latitude and longitude used to locate points on Earth.

Latitude (parallels)

Horizontal lines measuring distance north or south of the Equator (0° latitude).

Longitude (meridians)

Vertical lines measuring distance east or west of the Prime Meridian (0° longitude).

Prime meridian / International Date Line

The prime meridian (0°) runs through Greenwich, England; opposite it, the International Date Line (≈180°) marks where the date changes.

Map

A two-dimensional representation of Earth’s surface. Maps use symbols to convey geographic information. Key skills include map reading (interpretation), scale use, and projection effects.

Map projection

A mathematical method for representing the spherical Earth on a flat surface. All projections cause some distortion of shape, area, distance, or direction.

Distortion

A change in the shape, size, or position of features on a map due to projection. Different projections minimize some distortions at the expense of others.

Map scale

The relationship between distance on the map and distance on Earth (can be written, graphic, or ratio). A larger-scale map covers a smaller area with more detail.

Thematic map

A map that emphasizes a particular theme or attribute (e.g., population, climate, land use). Examples include dot maps, choropleth maps, and isoline (contour) maps

Choropleth map

Uses shading or coloring of predefined areas (like countries or states) to show intensity of a variable (e.g., population density).

Dot map

Uses dots to represent the frequency or density of a phenomenon in a region (each dot = a certain number of occurrences).

Isoline map (contour map)

Uses lines that connect points of equal value (e.g., elevation, temperature).

Cartogram

A map in which the sizes of geographic units are distorted proportionally to a statistical value (e.g., country size scaled by population).

Mental map

An individual’s internal representation of a portion of Earth’s surface (what a person knows and remembers about a place).

Model

A simplified representation or simulation of reality (often mathematical or visual) used to explain spatial patterns or processes (e.g., the Demographic Transition Model or Von Thünen’s model).

Time zones

Regions on Earth roughly 15 degrees of longitude wide, each set to a standard time (local times differ by hour across zones). Time zones facilitate synchronization of time over distances.

Population

All the inhabitants of a given place or area (country, city, region). Population geography studies their distribution, composition, and growth

Population density

a measurement of the number of people living in a given unit of area -usually per square kilometer or square mile.

Population distribution

The pattern of where people live. It is often uneven, influenced by terrain, climate, resources, and economy.

Population explosion

A very rapid population increase (as in the 20th century), typically due to high birth rates or declining death rates.

Doubling time

The number of years it takes for a population to double in size at its current rate of growth.

Rate of natural increase (RNI)

The difference between birth rate and death rate (usually expressed as a percentage); it excludes migration.

Population pyramid

A bar graph showing the age and sex structure of a population. It reveals birth rates, death rates, and demographic trends (e.g., expanding, constrictive).

Demographic transition model (DTM)

A model describing population change over time through stages (from high birth/death rates to low rates), explaining the shift from slow to fast to slow growth as a country develops.

Demographic regions

Geographic areas grouped by demographic characteristics (e.g., stage of the DTM, fertility, or growth rates).

Demographic momentum

Continued population growth after fertility declines, due to a previously youthful age structure (many people in childbearing years).

Cohort

A population group unified by a specific time- or age-related characteristic (commonly used for age cohorts in population pyramids, e.g., all 15–19-year-olds).

Dependency ratio

The ratio of people typically not in the labor force (young and elderly) to those typically in the labor force (ages 15–64). A higher ratio means more dependents per working adult.

Carrying capacity

The maximum population size that an environment can sustain indefinitely, given the food, habitat, water, and other resources available.

Ecumene

The portion of Earth’s surface occupied by permanent human settlement. Areas outside the ecumene include deserts, high mountains, forests, and tundra (sparsely settled regions).

Population projection

Estimates of future population size, age, and sex distribution, based on current data and trends.

Overpopulation

A situation where the number of people exceeds the capacity of the environment to sustain them (often measured by lack of resources or high population density relative to arable land).

Standard of living

The level of wealth, comfort, material goods, and necessities available to a certain socioeconomic class in a geographic area. Often correlated with development indicators.

Sustainability (population)

Practices that meet the needs of the present without compromising future generations; in population terms, often refers to stabilizing population growth to preserve resources.

Crude birth rate (CBR or natality)

The number of live births per 1,000 people in a population per year.

Crude death rate (CDR or mortality)

The number of deaths per 1,000 people in a population per year.

Infant mortality rate

The number of infants (under age 1) dying per 1,000 live births in a given year; a key indicator of population health.

Life expectancy

The average number of years a person can expect to live, often given at birth for a population. (Low life expectancy indicates high mortality, often in developing countries.)

J-curve

A graph illustrating exponential (rapid) growth. Used to describe Malthusian theory about population outpacing resources.

S-curve

An S-shaped graph showing logistic growth, as in the DTM or population reaching environmental limits (initially slow, then fast growth, then leveling off).

Maladaptation

A feature that is (or has become) more harmful than helpful, often referring to cultural practices unsuited to the environment (opposite of an adaptive strategy).

Malthus, Thomas

An 18th-century scholar who argued that population grows geometrically while food production grows arithmetically, leading to inevitable shortages unless checked (via famine, disease, or moral restraint).

Neo-Malthusian

Advocates of modern population control (e.g., birth control) who argue, like Malthus, that overpopulation leads to resource depletion and conflict.

Demographic equation

The formula P2 = P1 + (births – deaths) + (immigrants – emigrants), which accounts for population change between two periods.

Demographic transition

The change in a country’s population structure from high birth/death rates to low birth/death rates as it industrializes and develops.

Demographic transition model (DTM)

is a theory that explains how population changes over time based on economic development. It shows how birth rates and death rates affect population growth in five distinct stages

Forced migration

Permanent movement compelled by cultural or environmental factors (e.g., refugees fleeing war, or people displaced by natural disaster).

Voluntary migration

The migrant has chosen to move, usually for economic or personal reasons (e.g., jobs, family).

Internal migration

Movement of people within a country’s borders (e.g., rural-to-urban migration).

Interregional migration

Migration from one region to another (e.g., Southeast to Southwest within a country).

Intraregional migration

Movement within the same region (e.g., from inner city to suburbs).

Pull factors

Conditions that attract migrants to a place (e.g., jobs, freedom, climate).

Push factors

Conditions that drive people away from a place (e.g., poverty, war, drought).

Push-pull factors

Combined forces (from origin and destination) that induce migration.

Gravity model

A model predicting the level of interaction (including migration) between two places based on their population sizes and distance (interaction ~ population₁×population₂ / distance²). Large, close cities have more interaction.

Migration stream

A constant flow of migrants between two places (origin and destination). Patterns include chain migration (following family/friends), step migration (small moves toward final destination), seasonal migration, etc.

Chain migration

Movement of people to a destination where relatives or members of the same nationality previously migrated.

Step migration

A series of small moves that cumulatively result in a long-distance migration (e.g., farm → village → town → city).

Transhumance

Seasonal migration of livestock between mountains (summer) and lowland pastures (winter).

Periodic movement

Seasonal or cyclical movements (e.g., seasonal agricultural work, nomadism) that occur over periods.

Cyclic movement

Daily or seasonal routines (e.g., commuting, nomadic herding) in which people return periodically to a starting point.

Activity space

The local area within which people move or travel in the course of their daily activities (home, school, work).

Space-time prism

The set of all points that can be reached by an individual given the constraints of time and transportation; it illustrates accessibility.

Refugee

A person who flees to another country to escape persecution or disaster and is granted protection there. (Different from an internally displaced person, who stays within their home country.)