Imperial gallon (gal)
Definition: Imperial gallon na British volume unit wey equal exactly 4.54609 liters.
History/origin: Dem standardize imperial gallon for United Kingdom for 1824 as part of imperial measurement system.
Current use: Imperial gallons still dey show for some UK and Commonwealth contexts, especially for historical references, fuel economy, and some product descriptions.
Cubic kilometer (km³)
Definition: Cubic kilometer na huge metric volume unit. One 1 km × 1 km × 1 km cube get 1,000,000,000 m³, or 1,000,000,000,000 L.
History/origin: Earth science need readable unit for very big natural volumes, so km³ help for water bodies, ice, rock, magma, and atmosphere-scale quantities.
Current use: km³ dey show for hydrology, climate reports, ocean volume estimates, glacier studies, volcanic eruption data, reservoir capacity, and large-scale geography.