it is poured. (At the time, surface tension was not well understood.) The minim came with a set of procedures for ensuring accurate measurement, specifically, diluting powerful medicines that had previously been measured by the drop, then using a "minimometer" or "minim glass" (graduated pipette) with minim marks at regular intervals. The minim was defined as one 60th of a fluid dram or one 480th of a fluid ounce. This is equal to about 61.6 μL (U.S.) or 59.2 μL (Britain). Pharmacists have since moved to metric measurements, with a drop being rounded to exactly 0.05 mL (50 μL, that is, 20 drops per milliliter). In hospitals, intravenous tubing is used to deliver medication in drops of various sizes ranging from 10 drops/mL to 60 drops/mL. A drop is abbreviated gtt, with gtts used for the plural, often seen on prescriptions. Other sources abbreviate gt for singular, and gtt for plural. These abbreviations come from gutta (plural guttae), the Latin word for drop. See also Drop (liquid) References Units of volume Cooking weights and measures Metricated units