The total quantity or weight of organisms in a given area or volume 

The using up of a resource 

The strength and vitality required for sustained physical or mental activity 

a device that produces a continuous electric directly from the oxidation of a fuel, as 

that of hydrogen by oxygen

Of or relating to the nucleus of an atom 

The presence in or introduction into the environment of a substance or thing that has harmful 

or poisonous effects

The ability to do something or act in a particular way, esp. as a faculty or quality