Cubic foot (ft³)
Definition: A cubic foot is the volume of a cube with sides of one foot. It equals about 28.3168 liters.
History/origin: The cubic foot became standard in construction, trade, and utilities where larger everyday volumes needed a familiar imperial unit.
Current use: Cubic feet are used for refrigerators, freezers, room air flow, natural gas usage, and shipping volume.
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.