Cohorts refer to groups of individuals who are studied together over a period of time in order to observe trends, patterns, and changes in behavior, health, or other characteristics. Cohort studies are often used in epidemiology to track the development of diseases or conditions over time, as well as in social sciences to understand how individuals change and evolve in response to various factors. Cohorts can be defined by a variety of criteria, such as age, location, occupation, or exposure to certain risk factors. By following cohorts over an extended period, researchers can gain valuable insights into the causes and effects of various phenomena.