Population density is defined as:

• A. The number of people in a country.
• B. The average number of people living in a specific unit of area.
• C. The total land area of a region.
• D. The growth rate of the population.

Answer: (B)

Measuring how crowded an area is comes from looking at the ratio of people to land area. Population density is the average number of people living in a specific unit of area, such as per square kilometer or square mile. This makes it possible to compare places of different sizes and to plan for housing, schools, and services. For example, if 2 million people live in 400 square kilometers, the density is 5,000 people per square kilometer. The other descriptions describe total population, land area, or growth rate—distinct ideas from density.