Citizenship is the status of a person recognized under the custom or law as being a legal member of a sovereign state. A person may have multiple citizenships and a person who does not have citizenship of any state is said to be stateless.
Nationality is often used as a synonym for citizenship in English – notably in international law – although the term is sometimes understood as denoting a person's membership of a nation (a large ethnic group). In some countries, e.g. the United States, the United Kingdom, nationality and citizenship can have different meanings (for more information, see Nationality versus citizenship).
Each country has its own policies, regulations and criteria as to who is entitled to its citizenship. A person can be recognised or granted citizenship on a number of bases. Usually citizenship based on the place of birth is automatic; in other cases an application may be required.
Many thinkers point to the concept of citizenship beginning in the early city-states of ancient Greece, although others see it as primarily a modern phenomenon dating back only a few hundred years and, for mankind, that the concept of citizenship arose with the first laws. Polis meant both the political assembly of the city-state as well as the entire society. Citizenship has generally been identified as a western phenomenon. There is a general view that citizenship in ancient times was a simpler relation than modern forms of citizenship, although this view has come under scrutiny. The relation of citizenship has not been a fixed or static relation, but constantly changed within each society, and that according to one view, citizenship might "really have worked" only at select periods during certain times, such as when the Athenian politician Solon made reforms in the early Athenian state.