the number of people living per unit of an area (e.g. per square mile); the number of people relative to the space occupied by them
The population density of the Union is 25.6 to the square mile.
Our population density is fifteen hundred to the square mile.
No precise measurement of the population density on the study area was obtained.
As many as five adults have been caught in a trap simultaneously at times when the population density was high.
This indicates that the population density from 1967 to 1969 may have been higher than from 1948 to 1953.
The peak of reproductive activity slightly preceded the highest level of population density in each year (Fig. 8).