Fluid dram
The dram (alternative British spelling drachm; apothecary symbol ʒ or ℨ; abbreviated dr) was originally both a coin and a weight in ancient Greece. It refers to a unit of mass in the avoirdupois system, and both a unit of mass and a unit of volume in the apothecaries' system. The unit of volume is more correctly called a fluid dram, fluid drachm, fluidram or fluidrachm (abbreviated fl dr, ƒ 3, or fʒ).
A coin weighing one drachma is known as a stater, drachm, or drachma. The Ottoman dirhem was based on the Sassanian drachm, which was itself based on the Roman dram/drachm.
The British Weights and Measures Act of 1878 introduced verification and consequent stamping of apothecary weights, making them officially recognized units of measurement. By 1900, Britain had enforced the distinction between the avoirdupois and apothecaries' versions by making the spelling different:
In the avoirdupois system, the dram is the mass of 1⁄256 pound or 1⁄16 ounce. The dram weighs 875⁄32 grains, or exactly 1.7718451953125 grams.
In the apothecaries' system, which was widely used in the United States until the middle of the 20th century, the dram is the mass of 1⁄96 pounds apothecaries (lb ap), or 1⁄8 ounces apothecaries (oz ap or ℥) (the pound apothecaries and ounce apothecaries are equal to the troy pound (lb t), and troy ounce (oz t), respectively). The dram apothecaries is equal to 3 scruples (s ap or ℈) or 60 grains (gr), or exactly 3.8879346 grams.
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