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The prefixes of the international Système of units simplify the handling of measurements which have high reports/ratios of unit (for example, of 0,1 cm to 1000 m). These prefixes return to multiples and fractions of 10 or 1000.

Examples:

5 cm = 5 × 10-2 m = 5 × 0,01 m = 0,05 m

3 MW = 3 × 106 W = 3 × 1.000.000 W = 3.000.000 W

Note 1 : One calls Zillion S the numbers in “- it” and Zilliard S those in “- it”.

Note 2 : In data processing, it is more practical to use multiples in power of 2, one thus passes from a multiple to another while multiplying by 210, that is to say 1.024. The prefixes decaf and hecto, and those lower than the unit are not used in this field. However the units such as kilobit and gigaoctet, inter alia, are used in an incorrect way, though current. In data processing, the international electrotechnical Commission (CEI) recommends the use of prefixes such as kibi-, mébi and gibi, in order to avoid confusion - even between data processing specialists - between the Mo of the data processing specialists (1 024 × 1.024 bytes) and Mo/Mbit of the specialists network (1 000 × 1.000 bytes/bits) (in practice, the salesmen use as much as possible the most advantageous unit).

Historical evolution of the prefixes of IF

In the decree of the 18 germinal Year III (April 7th 1795), the prefixes Myria - and Myrio - explicitly formed part of the prefixes of the new decimal system (beside kilo, hecto- and decaf, déci-, centi- and milli-) . They mean ten thousand and one ten-thousandths, respectively. They were of use until in 1960.

The 11th General conference of the weights and measures (CGPM) drew up for the first time, in 1960, an official list of prefixes of IF, where myria- and myrio- did not appear any more. Belonged to the twelve official prefixes in 1960: “  téra-, giga-, méga-, kilo, hecto- and decaf, like déci-, centi-, milli-, microphone, nano and pico-  ”.

  • the 12th CGPM (1964) added “femto and atto-”.
  • the 15th CGPM (1975) added “péta- and exa-”.
  • the 19th CGPM (1991) added “zetta-, zepto- and yotta-, yocto-”.

Etymology of the prefixes

The first prefixes have an explicit significance:

  • Greek origin for the multiples: Deka (decaf) means “ten”, Hekaton (hecto-) means “hundred”, Khilihoi (kilo) means “thousand”, Murias (myria-, myrio-) means “dix-mille”.
  • origin Latin E for the submultiples: Decem (déci-) means “ten”, Centum (centi-) means “hundred”, thousand (milli-) means “thousand”.
The following suffixes were manufactured starting from words indicating of the large or small things:
  • large: in Greek, Megas (méga-) means “large”, Gigas (giga-) means “giant”, Teras (téra-) means “monster”;
  • small: Mikros (micro) means “small” in Greek, Nanus (nano) means “dwarf” in Latin, Piccolo (pico-) means “small” in Italian.
The multiple following was built starting from the resemblance enters will téra and Tétra (four in Greek), reinforced by the fact that 1012 = 103· 4 = 1  0004; there are thus Greek figures losing or gaining a letter:
  • Penta → péta-
  • Hexa → exa-
  • Octa → yotta- and yocto-

Other prefixes had thus been built in an abstract way ( Hepta → Hépa, Octa → Otta, nine in Greek → Néa, Déca → Déa) but never had official statute.

Finally:

  • Femtem (femto) means 15 in Danish (for 10-15).

  • Atten (atto-) means 18 in Danish (for 10-18).
  • Zetta- and zepto- are drawn from the French word seven because they represent 10±3· 7 = 1  000±7.

See too

Related articles

External bonds

  • Official list of the BIPM

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