| Term | Definition |
| Sex ratio | The number of males per 100 females |
| Doubling time | The number of years needed to double a population, assuming a constant NIR |
| Physiological density | The number of people per unit of arable land |
| Infant mortality rate | The total number of deaths in a year among infants under one year of age for every 1,000 live births in a society |
| Zero population growth (ZPG) | A decline in the total fertility rate to the point where the NIR is zero |
| Life expectancy | The average number of years a person can be expected to love, given current social, economic, and medical conditions. (Life expectancy at birth is the average number of years a newborn can be expected to live.) |
| Overpopulation | A situation in which the number of people in an area exceeds the capacity of the environment to support life at a decent standard of living |
| Natural increase rate (NIR) | The percentage of growth in a population in a year. The crude birth rate minus the crude death rate. |
| Epidemiology | The branch of medical science concerned with diseases that are prevalent among a population at a special time and are produced by some special causes not generally present in the affected area |
| Population pyramid | A bar graph that represents the distribution of population by age and sex |
| Epidemiological transition stage 3 | Degenerative diseases (moderately declining CDR): features more deaths caused by aging (cardiovascular disease and cancer) |
| Total fertility rate (TFR) | The average number of children a woman will have throughout her childbearing years |
| Epidemiological transition stage 4 | Delayed degenerative diseases (low but increasing CDR): medical innovations extend life expectancy for older people, although bad lifestyle choices cause conditions like obesity |
| Pandemic | Disease that occurs over a wide geographic area and affects a very high proportion of the population |
| Industrial Revolution | A series of improvements in industrial technology that transformed the process of manufacturing goods |
| Epidemiological transition stage 5 | A possible fifth stage that could be developing in which the CDR rises because most of the population is elderly and because of the re-emergence of diseases. Could be caused by evolution, poverty, and/or increased connections |
| Agricultural density | The ratio of the number of farmers to the total amount of land suitable for agriculture |
| Arithmetic density | The total number of people divided by the total land area |
| Epidemiological transition | Distinctive causes of death in each stage of the demographic transition |
| Demographic transition stage 4 | Low growth: the CBR declines to the point where it equals the CDR and the NIR approaches zero, features a TFR of about 2.1 |
| Demographic transition stage 3 | Decreasing growth: death rates stay low, and birth rates begin to drop |
| Demographic transition stage 1 | Low growth: hunting and gathering, high CBRs and CDRs, population increased when food was easily obtained, no full nation is in this stage |
| Demography | The scientific study of population characteristics |
| Epidemiological transition stage 1 | Pestilence and famine (high CDR): infections, parasitic diseases, and animal attacks were the main causes of death (ex: the Black Plague) |
| Crude death rate (CDR) | The total number of deaths per 1,000 living people |
| Crude birth rate (CBR) | The total number of live births per 1,000 living people |
| Epidemiological transition stage 2 | Receding pandemics (rapidly declining CDR): improved sanitation, nutrition, and medicine during the Industrial Revolution |
| Medical revolution | Medical technology invented in Europe and North America that has diffused to poorer counties in Latin America, Asia, and Africa. Improved medical practices have eliminated many traditional causes of death and allow people to live longer + healthier lives. |
| Demographic transition stage 2 | High growth: caused by the Industrial Revolution or the medical revolution |
| Ecumene | The population of Earth's surface occupied by permanent human setlement |
| Demographic transition | The process of change in a society's population from high birth and death rates and a low NIR to low birth and death rates, a low NIR, and higher total population |
| Dependency ratio | The number of people under 15 or over 64 compared to the number of people active in the labor force |
| Census | A complete enumeration of a population + the most important data tool for geographers. Controversial bc of nonparticipation (homeless + undocumented immigrants are less likely to take it) + sampling (you can't use census to redraw political boundaries) |
