Population size refers to the total number of individuals living in a particular area or region. It is an important demographic measure that helps to understand the scale and distribution of people within a given space, as well as their characteristics such as age, gender, race, and other factors. Population size can also be used to analyze trends over time, including changes in population growth rates, migration patterns, and birth and death rates. Understanding population size is important for planning and managing resources like healthcare, education, transportation, housing, and environmental protection, among others.