Aidan Stanger wrote:
Stephen Osborn wrote:

De facto a continuous built up area is a single _something_, the only
question is what. The phrase Metropolitan Area is used because these
somethings are relatively new and contain a number of things already
called cities.

The word you're looking for is conurbation. Or if it contains a number
of things already called cities, it's a megalopolis.

When I did my Human Geography back in the late 70's, a megalopolis was used
to describe where two 'metropolises' merge together rather than just an
aggregation of cities

ISTR the classical examples quoted were Minneapolis-St Paul as an
aggregation and the Boston-Washington corridor (or 'BosWash' - bleaugh!) as
a megalopolis