The UK gallon was originally set to be the volume occupied by 10 avoirdupois pounds of water at 60 degrees Fahrenheit.  It has been redefined as $4.54609$ liters.

For some time in the earlier half of the 20th century, the old Canadian gallon was defined $4.54607$ liters, differing in approximately $1$ part per quarter million.

A US liquid gallon is defined as $231$ cubic inches.

A US dry gallon is defined as the volume of a cylinder $1$ inch high and $18\frac{1}{2}$ inches in diameter, or $268.8025215$ cubic inches.

A drop or minim is defined as $\frac{1}{60}$ drachm.

A drachm or dram is defined as $\frac{1}{8}$ ounce.

A UK ounce is defined as $\frac{1}{160}$ UK gallon.

A US ounce is defined as $\frac{1}{128}$ US gallon.

A US tablespoon is defined as $\frac{1}{2}$ US ounce.

A UK tablespoon is defined as $15$ milliliters.

An Australian tablespoon is defined as $20$ milliliters.

A dessertspoon is defined as $2$ teaspoons.

A teaspoon is defined as $\frac{1}{3}$ tablespoon.

A pinch is defined as $\frac{1}{8}$ teaspoon.

A dash is defined as $\frac{1}{2}$ pinch.

A gill is defined as $\frac{1}{32}$ gallon.

A cup is defined as $\frac{1}{16}$ gallon.

A pint is defined as $\frac{1}{8}$ gallon.

A fifth is defined as $\frac{1}{5}$ gallon.

A quart is defined as $\frac{1}{4}$ gallon.

A pottle is defined as $\frac{1}{2}$ gallon.

A peck is defined as $2$ gallons.

A bucket is defined as $4$ gallons.

A bushel is defined as $8$ gallons.

A heaped bushel is defined as $1.278$ bushels.

A strike is defined as $2$ bushels.

A bag or sack is defined as $3$ bushels.

A coombe is defined as $4$ bushels.

A seam is defined as $8$ bushels.

A butt is defined as $15\frac{3}{4}$ bushels.

A last is defined as $80$ bushels.

A freight ton is defined as $40$ standard cubic feet.

A register ton is defined as $100$ standard cubic feet.

A UK barrel is defined as $36$ UK gallons.

A bulk barrel is defined as $5$ cubic feet.

A US dry barrel is defined as $105$ US dry quarts.

A US liquid barrel is defined as $126$ US liquid quarts.

A US barrel of petroleum is defined as $42$ US liquid gallons.

A UK barrel of petroleum is defined as $35$ UK liquid gallons.

A US barge of petroleum is defined as $1.05\times {10}^6$ US liquid gallons.

A UK barrel of petroleum is approximately $8$ parts per thousand less than a US barrel of petroleum.