The concentration can refer to any kind of chemical mixture, but most frequently refers to solutes and solvents in solutions. The molar (amount) concentration has variants, such as normal concentration and osmotic concentration.
con•cen•tra•tion (ˌkɒn sənˈtreɪ ʃən) n. 1. the act of concentrating or the state of being concentrated. 2. exclusive attention to one object; close mental application. 3. something concentrated: a concentration of stars. 4. (in a chemical solution) a measure of the amount of dissolved substance contained per unit of volume.