Yocto-

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Yocto- (symbol y) is an SI prefix in the SI system of units denoting a factor of 10⁻²⁴ or 0.000000000000000000000001.

Adopted in 1991, it comes from the Greek οκτώ, meaning eight, because it is equal to 1/1000⁸. As of 2007, yocto- is the smallest SI prefix to be confirmed.

It is used for measuring an atom's mass, for example:

• Mass of electron: 0.000 911 yg
• Mass of proton: 1.672 60 yg
• Mass of neutron: 1.674 90 yg

SI prefixes

1000n	10n	Prefix	Symbol	Since[1]	Short scale	Long scale	Decimal equivalent in SI writing style
10008	1024	yotta-	Y	1991	Septillion	Quadrillion	1 000 000 000 000 000 000 000 000
10007	1021	zetta-	Z	1991	Sextillion	Trilliard (thousand trillion)	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 (thousand billion)	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 (thousand million)	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
Notes: 1. The 1795 dates identify prefixes in use since the metric system was introduced. The other dates are not necessarily dates of first use, but rather the date of recognition by a resolution of the CGPM, which first met in 1889. 2. The micron was earlier recognized by the CGPM in 1948; that decision was abrogated in 1967-68.

[edit] See also

• SI prefixesbr:Yokto

ca:Yocto cs:Yokto es:Yocto fa:یوکتو fr:Yocto ko:욕토 it:Yocto nl:Yocto ja:ヨクト no:Yocto nn:Yocto nds:Yokto pl:Jokto pt:Yocto ksh:Yocto sl:Jokto sr:Јокто fi:Jokto sv:Yokto vi:Yóctô