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# Decametre

A decametre or dekametre (American spelling: decameter, earlier dekameter; symbol dam,, This measure is included in the SI mostly for completeness: in principle, any combination of prefix and unit can be written, but many are rarely used in practice. One practical use of the decameter is for altitude of geopotential heights in meteorology. Meteorologists also use another seldom encountered SI prefix: hecto- in hectopascal (hPa). The volumetric form (see below) cubic decametre is convenient for describing large volumes of water such as in rivers and lakes. The square decametre (dam2) also known as the are (a), is the basis for the hectare (100 dam2), the standard metric unit of land registry. 

## American English

American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States.

## Conversion of units

Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors.

## Deca-

Deca- or deka-, 1995, NIST Special Publication 811 (symbol da) is a decimal unit prefix in the metric system, denoting a factor of ten.

## Geopotential height

Geopotential height is a vertical coordinate referenced to Earth's mean sea level, an adjustment to geometric height (elevation above mean sea level) using the variation of gravity with latitude and elevation.

## Hectare

The hectare (SI symbol: ha) is an SI accepted metric system unit of area equal to a square with 100 meter sides, or 10,000 m2, and is primarily used in the measurement of land.

## Hecto-

Hecto- (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred.

## Imperial units

The system of imperial units or the imperial system (also known as British Imperial or Exchequer Standards of 1825) is the system of units first defined in the British Weights and Measures Act of 1824, which was later refined and reduced.

## International System of Units

The International System of Units (SI, abbreviated from the French Système international (d'unités)) is the modern form of the metric system, and is the most widely used system of measurement.

## Length

In geometric measurements, length is the most extended dimension of an object.

## Metre

The metre (British spelling and BIPM spelling) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in some metric systems, including the International System of Units (SI).

## Metric prefix

A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit.

## Metric system

The metric system is an internationally adopted decimal system of measurement.

## Orders of magnitude (length)

The following are examples of orders of magnitude for different lengths.

## Unit of measurement

A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity.

## United States customary units

United States customary units are a system of measurements commonly used in the United States.

## References

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