Liter
Definition: A liter (symbol: L) is a non-SI unit of volume equal to 1 cubic decimeter (1 dm³), or 1,000 cubic centimeters (1,000 cm³). It is closely related to the cubic meter.
History/Origin: First introduced in France in 1795 during the adoption of the metric system. The term 'liter' was derived from the older French unit 'litron'.
Current Use: Used worldwide for measuring liquids and bulk materials, including beverages, fuel, and household containers.
US Gallon
Definition: A U.S. gallon (symbol: gal) is a unit of volume in the U.S. customary system equal to 231 cubic inches or approximately 3.785 liters.
History/Origin: Originated from English wine gallons used in the 17th century. Standardized in the United States in 1832.
Current Use: Used primarily in the United States for measuring liquid commodities such as fuel and milk.