Urban sprawl takes place when:

Urban sprawl takes place when:

residential densities increase within an urban area.
an urban area expands into the countryside.
population of towns and cities decline due to out-migration.
a rural area expands into the neighbouring city.
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UPSC Geoscientist – 2021
Urban sprawl is characterized by the outward expansion of cities and their suburbs into the surrounding low-density rural land. It results in dispersed, low-density development with a heavy reliance on automobiles.
The key aspect of urban sprawl is the physical expansion of the urban area into previously non-urban (often countryside) areas.
Increased residential densities within an urban area (densification) is the opposite of sprawl. Population decline in cities due to out-migration might be a consequence or related phenomenon but is not the definition of sprawl itself. The phrase “a rural area expands into the neighbouring city” is inaccurate; it is the urban activities and built environment that expand into rural land.