An Ounce Is a Twelfth in One System and a Sixteenth in Another
An ounce is a unit of weight. Its size depends on the system, and the troy ounce used for gold is heavier than the everyday one.
An ounce is a unit of weight, and in the fluid sense a unit of volume. Two ounces are still in use and they differ: the everyday *avoirdupois* ounce is one sixteenth of a pound and weighs about 28.35 grams, while the *troy* ounce used for precious metals is one twelfth of a troy pound and weighs about 31.10 grams. Gold is quoted in the heavier one. The word comes from Latin *uncia*, a twelfth, which also gives *inch*.
- A unit of weight. *Four ounces of flour.*
- Troy ounce — used for precious metals. *A troy ounce of gold.*
- Fluid ounce — a volume unit. *Six fluid ounces.*
- Inch — from the same root. *One inch.*
- Latin — *uncia*, a twelfth. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | ounce | One ounce. |
| Plural | ounces | Eight ounces. |
| Symbol | oz | 8 oz. |
| Type | troy ounce | A troy ounce. |
| Latin | uncia | A twelfth. |
- Weigh out four ounces of butter.Cooking.
- Gold is priced per troy ounce.Markets.
- Inch and ounce share a root.Etymology.
Ounces that are not the same
- Avoirdupois ounce — 28.35 g, one sixteenth of a pound
- Troy ounce — 31.10 g, used for gold and silver
- UK fluid ounce — about 28.4 ml
- US fluid ounce — about 29.6 ml, slightly larger
- Not an ounce — the snow leopard, also called an ounce, an unrelated word
Old French *unce*, from Latin *uncia*, a twelfth part, from *unus*, one. The same word gives *inch*.
Why is gold measured in troy ounces?
Precious metals have used the troy system since medieval times. A troy ounce is about ten per cent heavier than an ordinary ounce.
Are ounce and inch related?
Yes. Both come from Latin uncia, a twelfth part, one of weight and one of length.