A litre (or liter) is a unit of volume in the metric system, commonly used for measuring liquids and sometimes solids. It's equivalent to 1,000 cubic centimeters (cm³) or one cubic decimeter (dm³). One litre of water at 4°C has a mass of approximately one kilogram. The symbol for litre is "l" or "L", with "L" being preferred by some to avoid confusion with the number one.