A metropolis is a word that means a very big city, that usually has over 500,000 people living in it. A metropolis often has many smaller towns and cities inside its area.
The word began in ancient Greece, originally meaning the city or state of origin of a colony. Later it came to mean the seat of a Bishop who also supervised the Church in other cities, or a city regarded as a center of some specified activity, or a large and important city. In India a "metropolis" is a city with more than a million people.