ounce: Definition, Synonyms and Much More from Answers.com
- ️Wed Jul 01 2015
This article is about Ounce (unit of mass). For Ounce (unit of force), see Pound-force. For all other uses, see Ounce (disambiguation).
The ounce (abbreviation: oz) is the name of a unit of mass in a number of different systems, including various systems of mass that form part of English units, Imperial units, and United States customary units. Its size can vary from system to system. The most commonly used ounces used today are the international avoirdupois ounce and the international troy ounce.
The abbreviation "oz" comes from the old Italian word "onza" (now spelled oncia), meaning ounce.
The distinction between mass and weight (or force), and its development, is discussed in the article on weight.
Summary of ounce units
Following table shows different ounce units in grams (SI):
Summary of ounce units| Ounce variant | Mass in grams |
|---|---|
| International avoirdupois ounce (most common) | 28.349 523 g |
| International troy ounce | 31.103 476 g |
| Apothecaries' ounce | Same as international troy ounce |
| Maria Theresa ounce | 28.066 8 g |
| Dutch metric ounce | 100 g |
| Chinese metric ounce | 50 g |
| Tael (East Asia) | Varying mass |
International avoirdupois ounce
An avoirdupois ounce is equal to 437.5 grains. There are 16 avoirdupois ounces in an avoirdupois pound. In 1958 the United States and countries of the Commonwealth of Nations defined the mass of the international avoirdupois pound to be 0.453 592 37 kilograms. Consequently, since 1958, the international ounce is defined to be equal to about 28.349 523 grams.
The ounce is commonly used as a unit of mass in the United States. While imperial units have been officially abolished in the United Kingdom, the ounce remains a familiar unit, especially amongst older people.
International troy ounce
A troy ounce (abbreviation: t oz) is equal to 480 grains. There are 12 troy ounces in a troy pound. Consequently, the international troy ounce is equal to about 31.103 476 grams.
Today, the troy ounce is used only to express the mass of precious metals such as gold, platinum or silver.
For historical measurement of gold,
- a fine ounce is a troy ounce of 99.5% (".995") pure gold
- a standard ounce is a troy ounce of 22 carat gold, 91.66% pure (11 "fine ounces" plus one ounce of alloy material)
Other ounces
Historically, in different parts of the world, at different points in time, and for different applications, the ounce (or its translation) has referred to broadly similar but different standards of mass (or weight, before the distinction between weight and mass developed). Some of these other ounces are described below.
Apothecaries' ounce
An apothecaries' ounce defined by the now-obsolete apothecaries' system of mass. This ounce was the same size as the troy ounce, and its symbol was ℥ ({{U+}}2125).
Maria Theresa ounce
"Maria Theresa ounce" was once introduced in Ethiopia and some European countries, which was equal to the weight of one Maria Theresa thaler, or 28.0668 g. Both the weight and the value are the definition of one "Birr", still in use in present-day Ethiopia and Eritrea.
Metric ounces
Some countries have redefined their ounces to fit in with the metric system.
The Dutch have redefined their ounce (in Dutch, ons) as 100 grams. Also the Avoirdupois pound (in Dutch pond) was redefined to 500 grams. This was adopted along with the introduction of the metric system and remains in informal usage (mostly in cookery and groceries).
East Asia has a traditional ounce, known as a tael, of varying value. In China, it has been given a metric value of 50 grams.
References
See also
External links
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