1630s, "action of bringing to a center," noun of action from verb concentrate (v.). Meaning "a mass so collected" is from 1670s; "continuous focus of mental activity" is from 1846.
concentration con·cen·tra·tion (kŏn'sən-trā'shən)
n.
An increase of the strength of a pharmaceutical preparation by the extraction, precipitation, and drying of its crude active agent.
An increase in the strength of a fluid or gas in a mixture by purification, evaporation, or diffusion.
The amount of a specified substance in a unit amount of another substance.