In India, cities are differentiated on the basis of population size. A metropolitan city is one which has a population between 1 million (10 lakh) and 5 million (50 lakh), and more than 5 million a city becomes mega city. Majority of metropolitan and mega cities are urban agglomerations, but it is not true the other way around.

Urban agglomerations arise when a metropolitan or mega city, due to limited space outgrowths its natural boundaries to encompass the towns/cities around it.

To Remember

Class 5<Class 4<Class 3<Class 2<Class 1<Metropolitan City<Megacity

Urban agglomeration is a type of mega city or a metropolitan, it is defined on the basis of population size but its formation. But UA’s inevitably are the largest in terms of population size, i.e., population growth induced expansion leads to Urban Agglomeration.