Demography involves the statistical study of human populations. As a very general science, it can analyze any kind of dynamic living population, i.e., one that changes over time or space (see population dynamics).

It encompasses the study of the size, structure, and distribution of these populations, and spatial and/or temporal changes in them in response to time, birth, migration, aging, and death. Demo- from Ancient Greek δῆμος dēmos, means “the people” and -graphy from γράφω graphō, implies writing, description, or measurement.

Demographics are quantifiable characteristics of a given population. Demographic analysis can cover whole societies, or groups defined by criteria such as education, nationality, religion, and ethnicity. Educational institutions usually treat demography as a field of sociology, though there are a number of independent demography departments.

Formal demography limits its object of study to the measurement of population processes, while the broader field of social demography or population studies also analyzes the relationships between economic, social, cultural, and biological processes influencing a population.