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This article is about the SI prefix. For other uses, see Tera.

Look up tera- in Wiktionary, the free dictionary.

tera (symbol: T) is a prefix in the International System of Units (SI) denoting 10¹², or 1,000,000,000,000 (1 trillion in short scale).

Confirmed in 1960, it comes from the Greek τέρας, meaning monster.^[1] 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 1,000.

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.

SI prefixes
1000^m	10ⁿ	Prefix	Symbol	Since^[1]	Short scale	Long scale	Decimal
1000⁸	10²⁴	yotta	Y	1991	Septillion	Quadrillion	1000000000000000000000000
1000⁷	10²¹	zetta	Z	1991	Sextillion	Trilliard	1000000000000000000000
1000⁶	10¹⁸	exa	E	1975	Quintillion	Trillion	1000000000000000000
1000⁵	10¹⁵	peta	P	1975	Quadrillion	Billiard	1000000000000000
1000⁴	10¹²	tera	T	1960	Trillion	Billion	1000000000000
1000³	10⁹	giga	G	1960	Billion	Milliard	1000000000
1000²	10⁶	mega	M	1960	Million		1 000 000
1000¹	10³	kilo	k	1795	Thousand		1000
1000^²⁄₃	10²	hecto	h	1795	Hundred		100
1000^¹⁄₃	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		0.000001
1000⁻³	10⁻⁹	nano	n	1960	Billionth	Milliardth	0.000000001
1000⁻⁴	10⁻¹²	pico	p	1960	Trillionth	Billionth	0.000000000001
1000⁻⁵	10⁻¹⁵	femto	f	1964	Quadrillionth	Billiardth	0.000000000000001
1000⁻⁶	10⁻¹⁸	atto	a	1964	Quintillionth	Trillionth	0.000000000000000001
1000⁻⁷	10⁻²¹	zepto	z	1991	Sextillionth	Trilliardth	0.000000000000000000001
1000⁻⁸	10⁻²⁴	yocto	y	1991	Septillionth	Quadrillionth	0.000000000000000000000001
The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM. The 1948 recognition of the micron by the CGPM was abrogated in 1967.

[edit] References

^ YourDictionary.com, tera, Retrieved on 2007-06-05.

[edit] See also

[0] YourDictionary.com, tera, Retrieved on 2007-06-05.

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