Know how to use "fewer" and "less"? Find out.
concentration con·cen·tra·tion (kŏn'sən-trā'shən)
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.