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drop

1

In Scotland, various units of mass, all 1/16th of an ounce:

In Scottish troy weight, for gold and silver, = ¹⁄₁₉₂ troy pound, about 1.944 grams; for various other commodities, = ¹⁄₂₅₆ troy pound, about 1.928 grams.

In Scottish trone weight, ¹⁄₃₂₀ trone pound, about 1.928 grams (about 29.75 English troy grains).

2

In English, a measure of capacity used in cooking and medicine. It has no definite volume. The size of a drop depends on such factors as the nature of the liquid, the material from which the dropper is made (does the liquid “wet” that material?), the dimensions of the dropper, the pressure on the liquid, any movement of the dropper, and other factors.

Physicians have long recognized that the drop is a very variable volume:

One drop of water ... One minim.
One drop of oils and tinctures ... About one-half minim.
One drop of chloroform ... About one-third minim.¹

For extensive examples of the sizes of drops of medicines, see this 1895 German study.

In dispensing medicine, these variables are controlled to some extent by supplying a specific dropper with the pharmaceutical. Obviously, the patient should not substitute a different medicine dropper.

1. The Monthly Review of Dental Surgery, Vol. V, June 1876 to May 1877.
London: Smith, Elder and Co., 1877.
Page 400,

3

In meteorology, the sizes of the drops of water in clouds and precipitation are used to characterize them. Drizzle, for example, consists of a fall of drops with diameters less than 0.5 millimeter.