litre

The litre (symbol L or l) is a unit of volume in the metric system, defined as one cubic decimeter (dm^3). It is not an SI base unit, but it is accepted for use with SI. One litre equals 1000 cubic centimeters (cm^3) and 0.001 cubic meters (m^3). The relationship to the cubic meter makes the litre convenient for measuring liquids and beverages.

The litre originated in the late 18th century in France, where it was introduced by the French Academy of Sciences as part of the metric system. Historically, it was associated with the volume occupied by one kilogram of water under specified conditions. In modern practice, the precise definition is 1 L = 1 dm^3, established by international agreement, so the litre is defined in terms of cubic decimeters rather than a mass of water.

Usage and notation vary by region. The symbol L is widely used to avoid confusion with the numeral 1, though the lowercase l is also common. The litre is widely employed in everyday life and commerce for liquids, such as beverages and fuel, as well as in cooking and industry. In scientific contexts, milliliters (mL) and cubic centimeters (cm^3) are frequently used alongside liters.

Spelling differs by language: British English uses litre, American English uses liter, and many other languages have their own forms. The litre remains a practical non-SI unit accepted for use with SI.