The state is a political ruling and management organization backed by violence, which is organized by the economically dominant class in accordance with the principle of regional division in order to safeguard and realize the common interests of the ruling class. This is the Marxist definition of a country, and you can judge the difference between a modern country and a medieval dynasty from this essential definition. Countries have different historical types at different stages of historical development. China in past dynasties and now are two different historical types of the same country, namely feudal country and socialist country.