Social systems depend upon stable expectations.
Individuals must be able to anticipate how others are likely to behave if coordination is to remain possible across time.
Norms provide this continuity.
They establish shared expectations concerning acceptable, expected, or appropriate forms of behaviour within a group.
Norms therefore reduce uncertainty and stabilise social interaction.
Because norms can be learned, transmitted, reinforced, and modified, they allow continuity to extend beyond individual organisms and immediate situations.
Social continuity depends not only upon communication but upon the persistence of shared expectations.
Norms are one of the principal mechanisms through which coordination becomes stable across generations.