Final answer:
The frequency of occurrence of something within a specifically defined area is known as distribution, which details the spatial arrangement of individuals or items. It is different from population density, which simply measures the average number per unit area.
Step-by-step explanation:
The frequency of occurrence of something within a specifically defined area is referred to as distribution. When we talk about the context of population studies, this term is often used to describe how individuals or items are spread out over an area. There are different types of patterns of distribution in populations, such as clumped, uniform, or random, depending on a variety of factors including species characteristics and environmental conditions.
Population density, on the other hand, is the average number of individuals per unit of area or volume, which gives a general sense of how crowded an area might be. Population distribution, in contrast, provides more detail by showing the actual spatial arrangement of individuals within the habitat.