my geography marginalia

A city (civitas) is a multitude of people united by a bond of community, named for its ‘citizens’ (civis), that is, from the residents of the city (urbs) [because it has jurisdiction over and ‘contains the lives’ (contineat vitas) of many]. Now urbs (also “city”) is the name for the actual buildings, while civitas is not the stones, but the inhabitants.

Isidore of Seville, Etymologies, Book XV, ii. Public buildings (De aedificiis publicis)