in ancient Greece, country district or village, as distinct from a polis, or city-state. Dēmos also meant the common people (like the Latin plebs). In Cleisthenes' democratic reform at Athens (508/507 BC), the demes of Attica (the area around Athens) were given status in local and state administration. Males 18 years of age were registered in their local demes, thereby acquiring civic status and rights.

The demes of Attica were local corporations with police powers and their own property, cults, and officials. Members met to decide deme matters and kept property records for purposes of taxation. The bouletai (members of the Athenian Boule, or Council of 500) were selected from each deme in proportion to its size. Because the demes were natural districts in origin, their size varied considerably. There were about 150 demes in the 5th century BC and more than 170 later. A typical deme had three bouletai, but the largest had as many as 22.

The term deme continued to designate local subdivisions in Hellenistic and Roman times and was applied to circus factions at Constantinople in the 5th and 6th centuries AD.

in biogenetics, a population of organisms within which the exchange of genes is completely random; i.e., all mating combinations between individuals of opposite sexes have the same probability of occurrence. The deme usually is not a closed population but contributes individuals to neighbouring populations and receives immigrants from them.