a combining form used in the names of units of measurement which are 10−15 (one quadrillionth) smaller than the unit denoted by the base word.

Origin of femto-

< Danish, Norwegian femt(en) fifteen + -o-
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British Dictionary definitions for femto-



denoting 10 –15femtometer Symbol: f

Word Origin for femto-

from Danish or Norwegian femten fifteen
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

Medicine definitions for femto-



One quadrillionth (10-15):femtovolt.
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