Atto-

atto- (symbol a) is an SI prefix to a unit and means that it is 10⁻¹⁸ times this unit. Examples are one attosecond or one attometre (U.S. spelling attometer).

Adopted in 1964, it comes from the Danish atten, meaning eighteen.

See also

• SI prefix
• attometre
• attosecond
• attoparsec

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Last updated on Friday June 06, 2008 at 18:23:48 PDT (GMT -0700)
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