Definition of Gallon
Gallon means: A gallon is a large volume unit in US customary and imperial systems. US gallon and imperial gallon are not equal.
In kitchen language, the definition of Gallon should stay clear and stable. A term is useful only when everyone reading a recipe understands the same unit meaning and uses the same measurement context. This is why professional kitchens, test kitchens, and home bakers rely on standard definitions instead of guesswork. When a definition is consistent, conversion steps become simpler and ingredient planning becomes easier.
It is also important to separate what a term measures. Some terms describe mass, while others describe volume. Mixing those ideas without a clear conversion method causes common recipe errors. A correct definition creates the starting point for correct conversion and repeatable cooking outcomes.