A group of individuals with some characteristics in common in epidemiology, subjects who have in common a particular experience during a particular time span.

Cohort studies within epidemiology determine areas based on exposure status. Usually cohort study subjects should be disease free when the cohort study begins. The cohort study is assessed over time to determine the final outcome status. An example of a cohort study would be the investigation of a cohort of smokers and non-smokers over a period of time to approximate the commonness of lung cancer.

See also:
Epidemiology
Clinical trial