Definition of femto-

: one quadrillionth (10−15) part of femtosecond

History and Etymology for femto-

International Scientific Vocabulary, from Danish or Norwegian femten fifteen, from Old Norse fimmtān; akin to Old English fīftēne fifteen

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“Femto-.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/femto-. Accessed 13 Jul. 2020.

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