quart

Quart comes from the French quart, meaning one-quarter, from Latin quartus (fourth). Applied to liquid measure, a quart was one-fourth of a gallon. The word entered English in the fourteenth century and immediately inherited the gallon problem: since the English gallon came in multiple sizes (wine gallon, ale gallon, corn gallon), the quart came in multiple sizes too.

The American quart is one-quarter of the US gallon: 946.35 millilitres, or about 32 fluid ounces. The British Imperial quart is one-quarter of the Imperial gallon: 1,136.52 millilitres, or about 40 fluid ounces. The difference is not small — a British quart is twenty percent larger than an American one. A quart of milk in London and a quart of milk in New York are not the same amount of milk.

There is also a dry quart, used for measuring grain and produce. The US dry quart is 1,101.22 millilitres — larger than the US liquid quart but smaller than the Imperial quart. Strawberries at a farmers' market are sometimes sold by the dry quart. The word 'quart' can therefore mean at least three different volumes depending on context and country.

The metric system has made the quart largely obsolete outside the United States. Most recipes worldwide now specify millilitres or litres. But Americans still buy quarts of oil, quarts of paint, and quarts of ice cream. The French word for 'fourth' became an English word for a specific volume — except the volume is never quite specific enough.