A citizen is a member of a nation, state or republic, entitled by citizenship to various rights, "privileges, and immunities." American citizens, for example, are accorded the full protection of the United States and her civil liberties as embodied in the Constitution. The word "citizen" carries talismanic significance for the many legal immigrants to the free republics of the world, since citizenship carries such great benefits, and is obtained only through the immigration process.
Citizenship in History
Citizenship was especially important in the Roman world, where, deriving from the Roman Republic, citizenship meant freedom from arbitrary rules, caprices, and sham trials, which plagued the many despotisms of the ancient world. At the height of Roman power, the famous invocation, "I am a Roman citizen!," or, "cives Romanus sum," became a guarantee of safekeeping, justice, and fair play, even in the farthest provinces of the Roman Empire. It is to this authority that the apostle Paul famously appealed. 
- U.S. Constitution, Fourteenth Amendment.
- Acts 25:11