Fluid dram

For the related unit of currency, see Greek drachma.

The dram (alternative British spelling drachm; apothecary symbol ʒ; abbreviated dr)[1][2]:C-6–C-7[3] was originally both a coin and a weight in ancient Greece.[4] 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.[2] The unit of volume is more correctly called a fluid dram, fluid drachm, fluidram or fluidrachm (abbreviated fl dr, ƒ 3, or ).[1][2]:C-17[3][5][6][7]

Ancient unit of mass

The Ottoman dirhem was based on the Sassanian drachm, which was itself based on the Roman dram/drachm. Modern Armenian drams, the currency of the Republic of Armenia, share this origin.

Modern unit of mass

In the avoirdupois system, the dram is the mass of 1256 pound or 116 ounce.[2]:C-6 The dram weighs 87532 grains,[2]:C-6 or exactly 1.771845195-9-7-83 grams.[2]:C-14

In the apothecaries' system, which was widely used in the United States until the middle of the 20th century,[11] the dram is the mass of 196 pounds apothecaries (lb ap), or 18 ounces apothecaries (oz ap or ℥)[2]:C-7 (the pound apothecaries and ounce apothecaries are equal to the troy pound (lb t), and troy ounce (oz t), respectively).[2]:C-6–C-7 The dram apothecaries is equal to scruples (s ap or ℈) or 60 grains (gr),[2]:C-7 or exactly 3.8879346 grams.[2]:C-14

"Dram" is also used as a measure of the powder charge in a shotgun shell, representing the equivalent of black powder in drams avoirdupois.[12]

Unit of volume

The fluid dram is defined as 18 of a fluid ounce,[2]:C-5,C-7 and is exactly equal to:

• 3.696697109-913 ml in US customary units [3785.41784 ÷ 1024][2]:C-5,C-12
• 3.5516328129 ml in British Imperial units [4546.09 ÷ (160 × 8)][2]:C-7[13]

A teaspoonful has been considered equal to one fluid dram for medical prescriptions.[14] However, by 1876 the teaspoon had grown considerably larger than it was previously, measuring 80–85 minims.[15] As there are 60 minims in a fluid dram,[2]:C-5,C-7 using this equivalent for the dosage of medicine was no longer suitable.[15] Today's teaspoon is equivalent to approximately 1 13 US fluid drams,[2]:C-18 or 80 US minims.[2]:C-5

Dram is also used informally to mean a small amount of spirituous liquor, especially Scotch whisky.[4]