Fluid Drachm (fl dr)
Modern equivalent
3.5516 millilitres
One eighth of an imperial fluid ounce, used by apothecaries and chemists for compounding liquid medicines.
The fluid drachm sat between the minim and the fluid ounce in the apothecary scale, subdividing into sixty minims. It is frequently confused with the Scottish whisky dram, which shares the same etymological root but describes a pub measure of 25ml or 35ml, roughly ten times larger. Both descend from the Greek drachma, a coin weight that lent its name to units of mass and volume across the medical and drinking traditions alike.