1.1.1.33. A polity is a complete society, concerned with the whole of human life, that can attain to the greatest natural common goods.

"so it is natural for many villages to come together to form a city (πόλις), a complete or perfect society, which does not depend on any greater society to help it achieve its ends. Such complete societies (which we can call ‘polities’ or ‘commonwealths’) take many forms in different times and places, but they always include some kind of rule ordering them to the common good."