The total mass of living organisms present in a given area.

It may be specified for a particular species; such as, earthworm biomass or for a general category; such as, herbivore biomass.

Estimates also exist for the entire global plant biomass and measurements of biomass can be used to study interactions between organisms, the stability of those interactions, and variations in population numbers.

Whenever dry biomass is measured, the material is dried to remove all water before weighing.