''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 (''decimal fractions'') of th ...
unit prefix
A unit prefix is a specifier or mnemonic that is added to the beginning of a unit 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 ...
in the
metric system
The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...
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, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official s ...
(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, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whos ...
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 co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
is about 12 centimetres or 1.2 decimetres.
References
{{Reflist
SI prefixes