pound, unit ofavoirdupois weight, equal to 16 ounces, 7,000 grains, or 0.45359237kg, and oftroy andapothecaries’ weight, equal to 12 ounces, 5,760 grains, or 0.3732417216 kg. The Roman ancestor of the modern pound, thelibra, is the source of the abbreviationlb. Inmedieval England several derivations of thelibra vied for general acceptance. Among the earliest of these, theTower pound, so called because its standard was kept in the Royal Mint in theTower of London, was applied toprecious metals and drugs and contained 5,400 grains, or 0.350 kg, whereas the mercantile pound contained 6,750 grains, or 0.437 kg. The troy pound, believed to have originated inTroyes, France, superseded the lighter Tower pound in 1527 as the gold andsilver standard. Increased trade with France led also to the adoption of the 16-ounce avoirdupois pound in the 16th century to replace the mercantile pound.

The Britishmonetarypound is historically linked with the minting of silver coins (sterlings) from the Tower pound. Large payments were reckoned in “pounds of sterlings,” later shortened to “pounds sterling.”