micro-
From Wikipedia, the free encyclopedia
micro- (µ) is a prefix in the SI and other systems of units denoting a factor of 10−6 (one millionth).[1] Confirmed in 1960, the prefix comes from the Greek μικρός (mikrós), meaning "small".
The symbol for it is the micro sign µ, the Greek letter mu (μ). For historical reasons, these are two different characters in Unicode, which appear slightly different in some fonts. The micro sign is encoded in the "Latin-1 Supplement" range identical to ISO/IEC 8859-1 (since 1985), at U+00B5 (Unicode 1.0, 1991). The Greek letter is encoded in the Greek range at U+03BC.
In circumstances where only the Latin alphabet is available, the prefix is sometimes represented using the letter u as in "um" for µm, or "uV" for µV. In some contexts, such as pharmacy, micrograms are often written mcg. Neither variant is standard.
1000m | 10n | Prefix | Symbol | Since[1] | Short scale | Long scale | Decimal |
---|---|---|---|---|---|---|---|
10008 | 1024 | yotta- | Y | 1991 | Septillion | Quadrillion | 1 000 000 000 000 000 000 000 000 |
10007 | 1021 | zetta- | Z | 1991 | Sextillion | Trilliard | 1 000 000 000 000 000 000 000 |
10006 | 1018 | exa- | E | 1975 | Quintillion | Trillion | 1 000 000 000 000 000 000 |
10005 | 1015 | peta- | P | 1975 | Quadrillion | Billiard | 1 000 000 000 000 000 |
10004 | 1012 | tera- | T | 1960 | Trillion | Billion | 1 000 000 000 000 |
10003 | 109 | giga- | G | 1960 | Billion | Milliard | 1 000 000 000 |
10002 | 106 | mega- | M | 1960 | Million | 1 000 000 | |
10001 | 103 | kilo- | k | 1795 | Thousand | 1 000 | |
10002/3 | 102 | hecto- | h | 1795 | Hundred | 100 | |
10001/3 | 101 | deca- | da | 1795 | Ten | 10 | |
10000 | 100 | (none) | (none) | NA | One | 1 | |
1000−1/3 | 10−1 | deci- | d | 1795 | Tenth | 0.1 | |
1000−2/3 | 10−2 | centi- | c | 1795 | Hundredth | 0.01 | |
1000−1 | 10−3 | milli- | m | 1795 | Thousandth | 0.001 | |
1000−2 | 10−6 | micro- | µ | 1960[2] | Millionth | 0.000 001 | |
1000−3 | 10−9 | nano- | n | 1960 | Billionth | Milliardth | 0.000 000 001 |
1000−4 | 10−12 | pico- | p | 1960 | Trillionth | Billionth | 0.000 000 000 001 |
1000−5 | 10−15 | femto- | f | 1964 | Quadrillionth | Billiardth | 0.000 000 000 000 001 |
1000−6 | 10−18 | atto- | a | 1964 | Quintillionth | Trillionth | 0.000 000 000 000 000 001 |
1000−7 | 10−21 | zepto- | z | 1991 | Sextillionth | Trilliardth | 0.000 000 000 000 000 000 001 |
1000−8 | 10−24 | yocto- | y | 1991 | Septillionth | Quadrillionth | 0.000 000 000 000 000 000 000 001 |
[edit] References
- ^ Bureau International des Poids et Mesures (2006). The International System of Units (SI) (8th Edn). ISBN 92-822-2213-6.