Final answer:
A metropolitan area in the United States is defined as having a core urban area with a population of at least 50,000 people. Urban clusters with 10,000 to 50,000 people can be designated as Micropolitan Statistical Areas if they are commuting hubs.
Step-by-step explanation:
To be a metropolitan area in the United States under current definitions, there must be a core urban area with a population of at least 50,000 people. Smaller cities with populations ranging from 10,000 to 50,000 people are classified as "urban clusters" and, if they serve as a central point of commuting, they can be designated as a Micropolitan Statistical Area. A key criterion for these classifications is a minimum population density of 1,000 people per square mile. Large metropolitan areas, commonly referred to as megalopolises, incorporate multiple cities and their suburbs, demonstrating the high level of urbanization in the U.S. economy wherein about 80% of the population currently resides in metropolitan areas, which also includes the suburbs surrounding cities.