atto-

a combining form that enters into compounds denoting a unit one-quintillionth (10−18) the size of the unit named by the stem.

Origin of atto-

< Danish or Norwegian att(en) eighteen + -o-

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British Dictionary definitions for atto-

atto-

prefix

denoting 10 –18attotesla Symbol: a

Word Origin for atto-

from Norwegian, Danish atten eighteen

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for atto-

word-forming element meaning "one quintillionth," 1962, from Danish atten "eighteen" (a quintillion is 10 to the 18th power), related to Old English eahtatene (see eighteen).

atto- in Medicine

atto-

pref.

One quintillionth (10-18):attometer.