1. the weight (mass), number, or size per unit volume 2. biology the size of a population in relation to some unit of space —note density is usually expressed as the number of individuals or the population biomass per unit area or volume 3. range management the number of individuals per unit area —note density is not a measure of cover although in the past the term has been used to mean cover —see frequency 4. silviculture —see stand density This definition last updated 10/25/2008