Noun
a system of weights based on the 16-ounce pound (or 7,000 grains)
Source: WordNetOf these, the avoirdupois weight is the most common system used in the U.S., although Troy weight is still used to weigh precious metals. Source: Internet
Troy weight, avoirdupois weight, and apothecaries' weight are all built from the same basic unit, the grain, which is the same in all three systems. Source: Internet