#gallon__gal  United States liquid unit equal to 4 quarts or 3.785 liters
  supertype:  #United_States_liquid_unit  a unit of measurement of capacity for liquids officially adopted in the United States Customary System
  part:  #quart
  part of:  #bbl__barrel  any of various units of capacity; "a barrel of beer is 31 gallons and a barrel of oil is 42 gallons"
     part of:  #hogshead.British_capacity_unit  a British unit of capacity for alcoholic beverages

No statement uses or specializes #gallon; click here to add one.