AP Human Review :)

a region with one or more urban clusters of at least 10,000 people at its core

region with at least one urbanized area as its core

an urban area in the US with fewer than 50,000 inhabitants

a very large and densely populated city, particularly the capital or major city in a country/region

any self-governing place in the US that contains at least 2,500 people

The largest city in the world is

city cluster or supercity comprised of two or more metropolitan areas that merge together into a continuous urban region

a single, uninterrupted urban area

A city with a population of over twenty million people

A city with a population of over ten million