What is it called when two citys merge together?

The process of two cities merging together is known as "conurbation" or "urban amalgamation." It occurs when two or more previously separate urban areas grow and expand until their boundaries overlap and they effectively become a single continuous urban area. The result is a larger, more densely populated metropolitan region.

Here are some common terms associated with conurbation:

1. Metropolitan Area: A metropolitan area refers to a contiguous geographic region that includes an urban area and its surrounding suburbs and commuter towns. It is often defined based on population density and economic ties.

2. Urban Agglomeration: An urban agglomeration is a term used to describe a cluster of towns, cities, and smaller urban areas that are connected economically, socially, and geographically. It is similar to a conurbation, but the boundaries may be less clearly defined.

3. Megalopolis: A megalopolis is a term used to describe a vast, densely populated urban area that may consist of multiple cities, suburbs, and even smaller urban areas that have grown together over time. Examples of megalopolises include the Greater Tokyo Area in Japan and the Boston-Washington corridor in the United States.

4. Urban Sprawl: Urban sprawl refers to the uncontrolled and often low-density expansion of urban areas into surrounding rural areas. It can contribute to conurbation as cities and towns grow outward and eventually merge with neighboring communities.

The merging of cities is often influenced by various factors such as economic growth, population increase, transportation improvements, and changing urban planning policies. It can have significant impacts on infrastructure, land use, local economies, and community identities.