- 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-
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- denoting 10 –15femtometer Symbol: f
from Danish or Norwegian femten fifteen
- One quadrillionth (10-15):femtovolt.