Tera

Categories: SI prefixes

Tera (symbol: T) is a prefix in the SI system of units denoting 1012, or 1 000 000 000 000.

Confirmed in 1960, it comes from the Greek τέρας, meaning monster. It also bears a resemblance to the Greek prefix τετρα- meaning four; the coincidence of it signifying the fourth power of 1000 served as a model for the higher-order prefixes peta, exa, zetta and yotta, all of which are deliberately distorted forms of the Latin or Greek roots for the corresponding powers (fifth to eighth respectively) of 1000.

In computer science tera- can sometimes mean 1 099 511 627 776 (240) instead of 1 000 000 000 000, especially in the term terabyte. To avoid this ambiguity, the binary prefix tebi- has been introduced to signify 240, but this, in common with the other binary prefixes, is not currently in general use.

SI prefixes
10n Prefix Symbol Short scale Long scale Decimal equivalent
1024 yotta Y Septillion Quadrillion 1 000 000 000 000 000 000 000 000
1021 zetta Z Sextillion Trilliard (thousand trillion) 1 000 000 000 000 000 000 000
1018 exa E Quintillion Trillion 1 000 000 000 000 000 000
1015 peta P Quadrillion Billiard (thousand billion) 1 000 000 000 000 000
1012 tera T Trillion Billion 1 000 000 000 000
109 giga G Billion Milliard (thousand million) 1 000 000 000
106 mega M Million 1 000 000
103 kilo k Thousand 1 000
102 hecto h Hundred 100
101 deca, deka da Ten 10
100 none none One 1
10−1 deci d Tenth 0.1
10−2 centi c Hundredth 0.01
10−3 milli m Thousandth 0.001
10−6 micro µ (mu) Millionth 0.000 001
10−9 nano n Billionth Milliardth 0.000 000 001
10−12 pico p Trillionth Billionth 0.000 000 000 001
10−15 femto f Quadrillionth Billiardth 0.000 000 000 000 001
10−18 atto a Quintillionth Trillionth 0.000 000 000 000 000 001
10−21 zepto z Sextillionth Trilliardth 0.000 000 000 000 000 000 001
10−24 yocto y Septillionth Quadrillionth 0.000 000 000 000 000 000 000 001
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See also

es:Tera fr:Téra ko:테라 it:Tera (prefisso) nl:Tera ja:テラ no:Tera pl:Tera sl:Tera sr:Тера fi:Tera vi:Têra