Molarity is defined as the number of moles of solute per litre of solution and is denoted by M (e.g. one mole of solute in one litre of solution equates to a one molar solution). Molarity is the most common expression of concentration for solids of known molecular weight. A more common concentration range for solutions used in laboratory is millimolarity, denoted by mM.
For example: molarity of solution (mol.dm-3) = amount of solute in moles/volume of solution in dm3