US quart (qt)
Definition: A US quart is one quarter of a US gallon, equal to about 0.94635 liters.
History/origin: The quart developed as a practical subdivision of the gallon in English customary systems and remained common in North America.
Current use: US quarts are used for milk, oil, food containers, and household liquid products in the United States.
Cubic kilometer (km³)
Definition: The cubic kilometer is a huge metric volume unit. A 1 km by 1 km by 1 km cube contains 1,000,000,000 m³, or 1,000,000,000,000 L.
History/origin: Earth science needed a readable unit for massive natural volumes, so km³ became useful for water bodies, ice, rock, magma, and atmosphere-scale quantities.
Current use: Km³ appears in hydrology, climate reports, ocean volume estimates, glacier studies, volcanic eruption data, reservoir capacity, and large-scale geography.