Concentration

Concentration refers to how much of something there is in a given volume, commonly liquid or gas

This can be given for each solvent in mol.dm^-3 (mol/l)(M), this is its molar concentration.

Another useful measure of concentration is for all of the solutes in a solvent, osmolarity or osmolality

One mole of a compound contains 6.02 x 10²³ molecules, this is Avogadro's constant