Which term refers to the population per unit land area?

The term that refers to the population per unit land area is density. In urban planning and geography, density is a critical concept that helps assess how many people live in a specific area, typically measured in individuals per square kilometer or square mile. This measurement is significant for understanding spatial relationships in a given environment, such as determining the need for services, infrastructure, and resources.

Density provides insight into living conditions, urban sprawl, and the effects of population growth. It is foundational in discussions about urbanization, housing, and environmental impacts within different regions. The other options, while related to population studies, do not specifically denote this particular relationship of people to land area. Population refers broadly to the total number of individuals in a specified area, demographics encompass the statistical characteristics of populations, and urban population specifies the number of people living in urban areas without necessarily relating it to land area.