Definition 1: A group of persons who experience a certain event in a specified period of time. For example, the birth cohort of 1985 would be the people born in that year.
Source: OECD Glossary of statistical terms. In Handbook of Vital Statistics Systems and Methods, Volume 1: Legal, Organisational and Technical Aspects, United Nations Studies in Methods, Glossary, Series F, No. 35, United Nations, New York 1991.
Definition 2: A group of people sharing a common demographic experience who are observed through time. The cohort of persons born in the same year is known as a generation, while the cohort of persons married in the same year is called a marriage cohort or a marriage generation.
Source: Eurostat's Concepts and Definitions Database, RAMON- Eurostat, European Union.
Definition 3: Group of persons who jointly experience a series of events over a period of time. A school cohort is defined as a group of pupils who enter the first grade of a given cycle in the same school year.
Source: UIS Glossary, UIS- UNESCO.