Currently, the terms are all over the map. Literally and figuratively.

What we oversee are Cities (maybe Towns or Villages depending on size).

When we are independent, we are City-States.

We are not Nations until we join together. (The existing titles all seem to be related to historic nationalities, even though not all modern nation-states.)

Rulers who are unable to attract at least 4 other rulers by the time a new Harvest is awarded should revert to City-States, giving others the chance to attempt to form a nation.

Please drop the word "Civilizations" and "Civ", using it only to refer to the game itself.

The central building should be a Palace only while we are King or Prince of a Nation. It should be an Estate for Dukes (and Earls), and Manor for Barons and Lords -- and maybe Hovel for Peons....