Is yule a city?

Whan it has a seat----------------A City is a City when it is INCORPORATED....essentially, it then becomes a Buisness It makes money through taxes (property, Sales, etc.) otherwise, an area not...

Both which and what can be used

A city is a city because it was one the the important places in the world.

The plural form of city is cities.

It depends on the context of the word. If you are talking about more than one city (plural) then you would use cities. "I have lived in four different cities." If you are talking about possession...