At what population is a city considered suburban? Rural?

Question

At what population is a city considered suburban?

At what population is a city considered rural?

At what population is a city considered urban?

Answer 1

I think it is a density thing more than an absolute number.

Answer 2

This isn't quite what you were looking for but it appears that it is all done by density. The following information is how it is determined in Ohio. China does it differently as does many other countries. By the looks of what I've found out it is the responsibility of the different States rather than a national standard that differentiates the cities. It does not appear to be based on total population.

http://exurban.osu.edu/maps_ohio.htm

Urban:

High-density urban areas were defined as all block groups with population densities of 5,000 or more persons per square mile; this is equivalent to less than 1/3 acre per housing unit. Low-density urban was defined as all block groups with a density of 1,000 to 5,000 persons per square mile or 1/3 to 1.5 acres per housing unit.

The Census standard of 1,000 people per square mile serves as the dividing line between urban and suburban areas.

Suburban:

A density of 325 to 1,000 persons per square mile (1.5 to 5 acres per housing unit)

Rural:

Rural areas were all block groups with a population density of less than 40 persons per square