A megacity is usually described as having more than how many inhabitants?

A megacity is usually defined as a metropolitan area with a total population in excess of ten million people. 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.

As of 2015, there are 36 megacities in existence. The largest of these are the metropolitan areas of Tokyo and Shanghai, each of these having a population of over 30 million inhabitants, with 38.8 million and 35.5 million respectively. Tokyo is the world's largest metropolitan area, while Shanghai has the world's largest city proper population.

The term "megacity" entered common use in the late 19th or early 20th centuries, one of the earliest documented uses being by the University of Texas in 1904. Initially the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million.

The UN predicts there will be 41 megacities by 2030.