There are 16 dry ounces in a pound. The ounce is an imperial unit of weight, which has largely been replaced by the metric system outside the United States. The United States' customary measuring units, also known as Standard Units, are derived from the imperial system.
In the Avoirdupois system, the ounce weighs 28.35 grams. The Troy ounce, used to define the mass of precious metal, is slightly heavier at 31.10 grams. The fluid ounce is a unit of liquid volume. A fluid ounce is one-twentieth of a pint.
The word "ounce" has its origins in Middle English, and is derived from the Latin "uncia," meaning "twelfth part."