norm

Informal guideline about what is, or is not, considered normal social behaviour (as opposed to rules and laws, which are formal guidelines). Such shared values and expectations may be measured by statistical sampling and vary from one society to another and from one situation to another; they range from crucial taboos, such as those against incest or cannibalism, to trivial customs and traditions, such as the correct way to hold a fork. Norms play a key part in social control and social order.