Molar concentration

Molar concentration, or molarity, or simply concentration, is a term in physical chemistry. It measures the concentration of a solution or mixture.
In chemistry, the molar concentration, formula_1 is defined as the amount of a constituent formula_2 (usually measured in moles – hence the name) divided by the volume of the mixture formula_3:
The volume formula_3 in the definition formula_6 refers to the volume of the solution, "not" the volume of the solvent. One litre of a solution usually contains either slightly more or slightly less than 1 litre of solvent because when a substance dissolves in a solvent it causes volume of liquid to increase or decrease.
The reciprocal quantity represents the dilution (volume) which can appear in Ostwald's law of dilution.