''Deci'' (symbol d) is a
decimal
The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...
unit prefix A unit prefix is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units of various order of magnitude, sizes are commonly formed by the use of such prefixes. The Metric prefix, prefi ...
in the
metric system
The metric system is a system of measurement that succeeded the Decimal, decimalised system based on the metre that had been introduced in French Revolution, France in the 1790s. The historical development of these systems culminated in the d ...
denoting a factor of one tenth. Proposed in 1793,
and adopted in 1795, the prefix comes from the Latin , meaning "tenth". Since 1960, the prefix is part of the
International System of Units
The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
(SI).
A frequent use of the prefix is in the unit deciliter (dl), common in food recipes; many European homes have a deciliter measure for flour, water, etc. A common measure in engineering is the unit
decibel
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a po ...
for measuring ratios of
power and root-power quantities, such as sound level and electrical amplification.
;Example:
*The diameter of a
compact disc
The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then rele ...
is about 12 centimetres or 1.2 decimetres.
References
{{Reflist
SI prefixes