“A citizen is one who has the right to take part in the deliberative or judicial functions of the state.”Aristotel · Politica · -335 · cartea III, capitolul 1
Citizenship isn't inherited, it's exercised: whoever doesn't deliberate or judge is merely a resident.
Aristotle's definition shifts the emphasis from birth to function: a citizen is someone who can deliberate in the assembly and judge in the courts. It is not enough to be born in a place; you must hold real power over common affairs. A resident who pays taxes but cannot vote or serve on a jury is, by this definition, an inhabitant, not a citizen. Status is proven through exercise.
Why it matters A clear criterion for today's rights debates: it asks not who holds a passport, but who has a real voice in the decisions that concern them.