case–control study: an observational study design in which the history of a group of participants with a specific outcome (eg a disease) is compared with the history of a matched group without the outcome – for example, comparison of the previous drinking habits of people with cancer and people without cancer

cohort study: an observational study design in which a cohort of participants with a specific treatment, exposure or condition is followed over a period and compared with a matched group with a different treatment, exposure or condition – for example, comparison of the long-term outcomes of cohorts of children brought up in areas with and without fluoride in the drinking water