What is a fifth of liquor?

A fifth of liquor is a unit of volume used in the United States for alcoholic beverages. It is equivalent to one-fifth of a US gallon, which is approximately 757 milliliters or 25.6 US fluid ounces. While officially superseded by metric measurements like the 750ml bottle, the term "fifth" remains in common use, especially when referring to liquor bottles. It's a historical measurement rooted in the days when spirits were commonly sold in gallon jugs.