Meaning of apothecaries' weight

apoth'ecaries' weight"

Pronunciation: [key]
  1. a system of weights used chiefly in compounding and dispensing drugs: 20 grains = 1 scruple (&scruple;); 3 scruples = 1 dram (&yogh;); 8 drams = 1 ounce (&ounce;); 12 ounces = 1 pound. The grain, ounce, and pound are the same as in troy weight, the grain alone being the same as in avoirdupois weight.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.