Appendix:SI units

The International System of Units (abbreviated SI from French Système international d'unités ) is the modern form of the metric system and is a system of units of measurement devised around seven base units and the convenience of the number ten. It is the world's most widely used system of measurement, both in everyday commerce and in science.

SI consists of a set of units together with a set of prefixes. The units are divided into two classes&mdash;base units and derived units. There are seven base units, each representing a different physical quantity. The prefixes may be combined with the base units and derived units to describe the number of those units. For example, 3×10$0$ newton = 3 petanewton, combining the prefix peta-, for quadrillion, with the derived unit, newton.

SI units
SI is an abbreviation of Système International (d'Unités)    [International System (of Units)] and is a standard metric system of units adopted for official scientific use. For more information, see Wikipedia's article on SI.

'''Note: this page is simply a collection of links to the names of SI units and their prefixes and multiples. For further information, see the Wikipedia articles and '''.

Base units (with symbols in parentheses; see full descriptions below)

 * ampere (A)
 * candela (cd)
 * kelvin (K)
 * kilogram, (kilogramme) (kg)
 * metre (Commonwealth English), meter (US English) (m)
 * mole (mol)
 * second (s)

Derived units (with symbols in parentheses; see full descriptions below)

 * becquerel (Bq)
 * coulomb (C)
 * degree Celsius (°C)
 * farad (F)
 * gray (Gy)
 * henry (H)
 * hertz (Hz)
 * joule (J)
 * katal (kat)
 * lumen (lm)
 * lux (lx)
 * newton (N)
 * ohm (Ω)
 * pascal (Pa)
 * radian (rad) (classified as a supplementary unit until 1995)
 * siemens (S)
 * sievert (Sv)
 * steradian (sr) (classified as a supplementary unit until 1995)
 * tesla (T)
 * volt (V)
 * watt (W)
 * weber (Wb)

Alternative names for SI units and their multiples and submultiples

 * amp (for ampere)
 * cycle (alternate name for hertz)
 * Multiples:
 * kilocycle
 * megacycle
 * cycle per second (alternate name for hertz)
 * kilocycle per second
 * megacycle per second
 * kilo (short for kilogram)
 * micron (alternate name for micrometre)
 * fermi (alternate name for femtometre, sometimes used in nuclear physics)

Former names for SI units

 * degree Kelvin
 * new candle

SI prefixes
Notes:
 * 1. meg- is used before a vowel, as in megohm
 * 2. not commonly used

Binary prefixes
The following prefixes are not part of SI. They were adopted by the IEC to express binary multiples.

Former prefixes
These prefixes have been used informally at times, but were never part of SI.

Commonly used multiples of units

 * The table below shows which prefixes are most commonly used with each unit. In theory, any combination of a prefix and a unit is possible.  In practice, only those multiples that are of practical use are used.  Multiples towards the left and right of the table tend to gain currency as advances in technology and miniaturisation make them meaningful.


 * Links are to combinations that are in relatively common scientific use. Blank entries indicate combinations that are rare or not used.


 * Notes:


 * 1) Units are ordered alphabetically by their symbol. Prefixes are ordered from largest to smallest.
 * 2) It is the gram (g) that takes prefixes, not the kilogram.
 * 3) Some combinations have special names; for example, 106 grams is called a tonne, not a "megagram".
 * 4) The multiples in the grey columns are not in official scientific usage.
 * 5) The table lists multiples of SI units only. Other units that use the SI prefixes, such as kilobyte and millibar, are not given here.
 * 6) The table is currently incomplete. More links will be added later.

(Sources: ; Oxford English Dictionary, 2nd ed.)

Derived units with special names
Base units can be combined to derive units of measurement for other quantities. In addition to the two dimensionless derived units radian (rad) and steradian (sr), 20 other derived units have special names.

Other common units, such as the litre, are not SI units, but are accepted for use with SI.

Multiples of base units by prefix
Notes:
 * * : The kilogram is the SI base unit for mass, not the gram, which is obviously (1/1000) kilogram.
 * + : The candela is still considered an SI base unit, though it is no longer fundamental, being defined in terms of other SI units.

Finnish

 * yotta- = jotta-
 * zetta- = tsetta-
 * exa- = eksa-
 * peta- = peta-
 * tera- = tera-
 * giga- = giga-
 * mega- = mega-
 * kilo- = kilo-
 * hecto- = hehto-
 * deca- = deka-
 * deci- = desi-
 * centi- = sentti-
 * milli- = milli-
 * micro- = mikro-
 * nano- = nano-
 * pico- = piko-
 * femto- = femto-
 * atto- = atto-
 * zepto- = tsepto-
 * yocto- = jokto-


 * meter = metri
 * kilogram = kilogramma
 * second = sekunti
 * ampere = ampeeri
 * kelvin = kelvin
 * mole = mooli
 * candela = kandela


 * hertz = hertsi
 * joule = joule
 * watt = watti
 * volt = voltti
 * ampere = ampeeri
 * ohm = ohmi
 * farad = faradi
 * henry = henry
 * radian = radiaani
 * steradian = steradiaani
 * lumen = lumen
 * lux = luksi

French
In French, accents appear in the following prefixes and unit-names:


 * peta- = péta-
 * tera- = téra-
 * mega- = méga-
 * deca- = déca-
 * deci- = déci-


 * ampere = ampère
 * candela = candéla
 * meter = mètre
 * steradian = stéradian
 * second = seconde

German
In German, common nouns (including the names of SI units) are capitalized. Some spelling variations also appear:


 * hecto- = hekto-
 * deca- = deka-
 * deci- = dezi-
 * centi- = zenti-
 * micro- = mikro-
 * pico- = piko-
 * yocto- = yokto-


 * second = Sekunde
 * radian = Radiant
 * steradian = Steradiant

Greek

 * quetta- = κουεττα-
 * ronna- = ροννα-
 * yotta- = γιοττα-
 * zetta- = ζεττα-
 * exa- = εξα-
 * peta- = πετα-
 * tera- = τερα-
 * giga- = γιγα-
 * mega- = μεγα-
 * kilo- = χιλιο-
 * hecto- = εκατο-
 * deca- = δεκα-
 * deci- = δεκατο-
 * centi- = εκατοστο-
 * milli- = χιλιοστο-
 * micro- = μικρο-
 * nano- = νανο-
 * pico- = πικο-
 * femto- = φέμτο-
 * atto- = αττο-
 * zepto- = ζεπτο-
 * yocto- = γιοκτο-
 * ronto- = ροντο-
 * quecto- = κουέκτο-


 * meter = μέτρο
 * kilogram = χιλιόγραμμο
 * second = δευτερόλεπτο
 * ampere = αμπέρ
 * kelvin = κέλβιν
 * mol = μολ
 * candela = καντέλα

Spanish

 * hertz = hercio
 * joule = julio
 * watt = vatio
 * volt = voltio
 * ampere = amperio
 * ohm = ohmio
 * farad = faradio
 * henry = henrio
 * radian = radián
 * steradian = estereorradián