By definition, the term solution in chemistry refers to a homogeneous mixture. The mixture can include two or more different substances. Solutions can also exist in liquid, solid or gaseous states.
Alloys such as brass are examples of solid solutions. Salt dissolved in water creates a liquid solution. Air is an example of a gaseous solution. In aqueous solutions, water is considered the solvent and the material that is dissolved is the solute. In other liquid solutions, the solvent is the ingredient found in the greatest amount. The concentration of a solution usually refers to the mass per unit volume, as in grams per liter.