In analytical chemistry, a standard solution is a solution containing a precisely known concentration of an element or a substance, a known weight of solute is dissolved to make a specific volume. It is prepared using a standard substance, such as a primary standard. Standard solutions are used to determine the concentrations of other substances, such as solutions in titrations. The concentrations of standard solutions are normally expressed in units of moles per litre (mol/L, often abbreviated to M for molarity), moles per cubic decimetre (mol/dm³), kilomoles per cubic metre (kmol/m³) or in terms related to those used in particular titrations (such as titres). A simple standard is obtained by the dilution of a single element or a substance in a soluble solvent with which it reacts.