Ounce

The ounce is a unit used to measure weight or mass, and it comes from an old measuring system used by the Ancient Romans called the uncia. There are different kinds of ounces used today. One common type is the avoirdupois ounce, which equals exactly 28.349523125 grams, or about 1⁄16 of an avoirdupois pound. This is the kind of ounce most often used in the United States and in British measurements.

Another special kind of ounce is the troy ounce, which is a bit heavier at exactly 31.1034768 grams. The troy ounce is used when measuring valuable metals like gold, silver, platinum, and other precious materials.

The word "ounce" can also mean other things besides weight. For example, ounce-force is a way to measure push or pull, and fluid ounce is a way to measure how much liquid there is in a container. Throughout history, many different kinds of ounces were used in many places and for many different purposes.

Etymology

The word "ounce" comes from the Ancient Roman word uncia, which means "a twelfth." This was a unit of measurement that weighed about 27.4 grams, almost the same as an avoirdupois ounce today. The word uncia was borrowed into English in two different ways. First, it became the word "inch" in Old English. Later, it came into Middle English from Anglo-Norman and Middle French, giving us the word "ounce." The short form "oz" comes from the Italian word onza.

Definitions

Historically, the word "ounce" has been used in many places and times to measure weight, but the exact amount it means has changed a little bit.

Active use

International avoirdupois ounce

The international avoirdupois ounce (written as oz) is exactly 28.349523125 grams. This was decided in 1959 by an agreement between the United States and many other countries.

In this system, sixteen ounces make one pound. The ounce is still commonly used in the United States. In the United Kingdom, it is no longer an official unit, but people sometimes still use it to describe how much food they are serving, like in restaurants.

International troy ounce

Main article: Troy ounce

A troy ounce (written as oz t) equals 31.1034768 grams. There are twelve troy ounces in an old unit called a troy pound.

Troy ounces are used only for measuring precious metals like gold, platinum, palladium, rhodium, or silver. For example, coins made from these metals are often sold in troy ounces.

Metric ounces

Some countries changed their idea of an ounce to fit the metric system. For example, in Germany, an old type of ounce used by doctors was 30 grams.

In 1820, the Netherlands changed their ounce to equal 100 grams. Even though the official name for it was removed in 1937, many people still use this idea today. This same idea was also taught in schools in Indonesia and is listed as normal usage in their main dictionary.

Historical

Apothecaries' ounce

The apothecaries' ounce, which was the same size as the troy ounce, was once used by doctors but is no longer used.

Maria Theresa ounce

The "Maria Theresa ounce" was once used in Ethiopia and some European countries. It equaled the weight of a coin called the Maria Theresa thaler, or 28.0668 grams. This weight defined the value of the Ethiopian money unit called the birr, which is still used today.

Spanish ounce

Further information: Spanish customary units

In Spain, a pound was 460 grams, and an ounce was 1⁄16 of a pound, or 28.75 grams. It was also split into smaller parts called adarmes. For medical use, it was split differently into parts called dracmas.

Tower ounce

The Tower ounce was 29 grams and was used in English mints, especially the one in the Tower of London. It was stopped in favour of the Troy ounce by King Henry VIII in 1527.

Ounce-force

Main article: Pound-force

An ounce-force is a small unit of force. It equals one-sixteenth of a pound-force, or roughly 0.2780139 newtons. This force is what you would feel from a mass of one avoirdupois ounce pulling down due to gravity at sea level.

The word "ounce" in ounce-force refers to the avoirdupois ounce. This unit is sometimes used in engineering to make it easier to switch between measurements of mass, force, and movement. However, it is not used very often.

Fluid ounce

Main article: Fluid ounce

A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl.) is a unit of volume. An imperial fluid ounce is defined in British law as exactly 28.4130625 millilitres, while a US customary fluid ounce is exactly 29.5735295625 mL, and a US food labelling fluid ounce is 30 mL. The fluid ounce is sometimes called just an "ounce" in places like bartending.

Other uses

Ounces can also help us understand how heavy certain fabrics are. For example, when people talk about "16 oz denim," the number tells us how much a piece of that fabric weighs. This way, ounces help describe the thickness or heaviness of clothes like jeans.

In making electronic circuits, ounces are used to measure how thick a layer of copper is. When people say a layer is "1 oz," they mean it has a certain thickness when spread out over a specific area. This helps engineers make sure electronic parts work properly.

Notes and references