"A megalopolis (sometimes improperly called a megapolis) or megaregion is typically defined as a chain of roughly adjacent metropolitan areas. The term was used by Patrick Geddes in his 1915 book Cities in Evolution,[1] by Oswald Spengler in his 1918 book, The Decline of the West, and Lewis Mumford in his 1938 book, The Culture of Cities, which described it as the first stage in urban overdevelopment and social decline."
"A megacity is usually defined as a metropolitan area with a total population in excess of ten million people.[1] A megacity can be a single metropolitan area or two or more metropolitan areas that converge. The terms conurbation, metropolis and metroplex are also applied to the latter."
NYC alone is a megacity. The US northeast is a megalopolis.
An easy way to tell, I think: a megacity very likely has a single encompassing public transit authority, because the transit needs of the individual underlying municipalities involve a lot of "I live in this city, work in that city, and need to commute every day" and that can't be easily handled if it's a bunch of separate systems.
The Vancouver Metropolitan Area in British Columbia, for example, is six cities, with one transit system. There's also the Greater Vancouver Regional District, which is a megalopolis that consumes a few more adjacent cities, but those aren't linked by transit.
This doesn't always work, the Greater Toronto Area (GTA), even if you take the most narrow interpretation, is made up of a bunch of different transit systems. Walking along on Google Streetview, there is no way you could tell when on Yonge Street you have "left Toronto", and need to pay extra fare on TTC, or take YRT/Viva/Blue etc.
But it's a neat idea to think about transit and accessibility. I'd love to know at which point in the world you can reach the most people within an hour of transit for example, or two hours... This is the advantage in the Pearl River Delta (and probably Tokyo) - there is tons of high-speed rail, subways etc, so you can probably reach about 40 million within 1.5 hr (an hour high speed rail and half an hour on local transit). Whereas it takes me an hour and a half just getting to the airport in Toronto.
I like this. The next step down must surely be the Super City. In New Zealand the Auckland "Super City" would love to be a mega city. Auckland's fragmented and disconnected transport system, chaotic local government arrangements and expensive attempts at integration make it substantially less than a megacity. That and the low population count.
Oh I like that definition. Means that you'd count the Gold Coast and Brisbane (and Ipswich) together as a megacity, which is kinda true, as "South East QLD".
The GVRD renamed itself to the Metro-Vancouver about 5 or 6 years ago. The Vancouver Metro area is the exact same thing as the GVRD. They aren't different things.
"A megalopolis (sometimes improperly called a megapolis) or megaregion is typically defined as a chain of roughly adjacent metropolitan areas. The term was used by Patrick Geddes in his 1915 book Cities in Evolution,[1] by Oswald Spengler in his 1918 book, The Decline of the West, and Lewis Mumford in his 1938 book, The Culture of Cities, which described it as the first stage in urban overdevelopment and social decline."
vs megacity: http://en.wikipedia.org/wiki/Megacity
"A megacity is usually defined as a metropolitan area with a total population in excess of ten million people.[1] A megacity can be a single metropolitan area or two or more metropolitan areas that converge. The terms conurbation, metropolis and metroplex are also applied to the latter."
NYC alone is a megacity. The US northeast is a megalopolis.