Quote Originally Posted by vorropohaiah View Post
I was unaware that there's a standard for the demarcations between city sizes.
There is no standard demarcation, especially not in modern day where everything is considered a city or town regardless of actual population and more based on feel of the place.
The numbers I gave are general mideval demographic average numbers. There is no known reason why the numbers are roughly 0.2k, 2k, 20k, and 200k either, but I could take a running guess.

The reason you don't really need to separate city from fortified city is because fortified city is the standard. Walls as much keep people out as they do in and most major population centers have them. On the other hand a Fort has qualities of a city, but because it's purpose is different you wouldn't classify that in the same way and nor would you mention population there because the population there is less static than at a city.