a world city is city generally considered to be an important node in the global economic system. it's:economic, fashion media and arts, learning and resource center.
examples; london, tokyo, new york, dubai, sau paulo and shanghai.

millionaire cities, are cities with over 1 million inhabitants.

push factors from rural:
population growth, war and conflict, natural disasters, cash crops, health, lack of services, agricultural problems.

global pattern of urbanisation:
almost 50% of people live in towns and cities, 19% of us live in cities with over 1 million inhabitants, there are currently 20 mega cities, this is due to rapid urbanisation over the past 50 years as the LEDCs have been developing.