noun
gallon
A unit of volume; in Japan usually the US gallon (approx. 3.785 liters) or the British imperial gallon (approx. 4.546 liters). Context often clarifies which gallon is meant.
このタンクは10ガロンの水が入る。
This tank holds 10 gallons of water.
ガソリンを5ガロン入れてください。
Please put in 5 gallons of gasoline.