| femto- | |
| —prefix | |
| f denoting 10--15: femtometer | |
| [from Danish or Norwegian femten fifteen] | |
| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
| a chattering or flighty, light-headed person. |
femto- pref.
One quadrillionth (10-15): femtovolt.