Ounce (unit of mass)

1 ounce of gold.

The ounce (oz) is a unit of mass used since Ancient Rome to more accurately weigh merchandise and other items, especially if their weight was less than a roman pound The ounce is still commonly used in Anglo-Saxon countries, Puerto Rico and formerly its use was more widespread throughout Europe.

Origin of the term

The word ounce comes from the Latin ūncia, derived in turn from the Proto-Indo-European *oinoko- (from which, by the way, unique), suffixed form of the stem *oino- (from which one also derives). The ūncia was the fractional unit used by the Romans, who used duodecimal fractions; that is, it meant "a twelfth part." In the monetary context, the uncia was the coin of value corresponding to 1/12 of as. For its part, the ounce of weight was 1/12 of a pound (note that the 16-ounce pound is later than the 12-ounce pound). The English words ounce (ounce) and inch (inch = 1/12 foot) are also derived from ūncia.

English ounces in use

The ounce is called ounce in English, abbreviated oz and the symbol of the apothecaries' measurement system ℥ (Unicode U+2125). Currently only two types of ounce are used:

• La on avoirdupois (common use) is the sixteenth part of an avoirdupois pound, and is equivalent to 28,349 523 125 (veintiocho commas three hundred forty-nine million five hundred twenty-three thousand and twenty-five) grams, plus:
  • 437.5 grains
  • 16 dracmas avoirdupois
  • 0.0625 pounds avoirdupois

• La ounce troy (used only in jewellery, orfebrew and numismatic to weigh precious metals) is the twelfth part of a troy pound, and is equivalent to 31,103 476 8 grams, in addition to:
  • 480 grains
  • 20 pennyweights
  • 8 throy drachmas
  • 0.083 333 333 333 333 3 pounds troy

There is another Anglo-Saxon unit in use, called fluid ounce (fluid ounce, in English it is abbreviated fl. Oz), which is not mass but volume (or capacity, as it is colloquially referred to).

Ounces disused

• La Castilian ounce it was 28,7558 grams, and it was divided into 16 adarms; in pharmacy, it was divided into 8 dracmas; and in both cases, in 576 grains.

• La pharmaceutical was used in the pharmacies and in Anglo-Saxon pharmacology. It is the twelfth part of a pharmaceutical pound and is equivalent to 31,1034768 grams, in addition to:
  • 480 grains
  • 24 scruples
  • 8 pharmaceutical dracmas
  • 0.083333333333333333 pharmaceutical pounds