A mega city is a term used to describe an urban area with a population of over 10 million people. Other synonyms for mega city include metropolis, megapolis, and megalopolis. These terms are often used interchangeably and refer to the same type of urban area. Other synonyms that are less commonly used include hypercity, great city, and giant city. Regardless of the term used, a mega city represents a significant challenge for urban planners and policymakers due to issues such as traffic congestion, environmental pollution, and socio-economic inequality. Despite these challenges, mega cities remain important centers of innovation and economic activity.