femto-

combining form

: one quadrillionth (10−15) part of
femtosecond

Word History

Etymology

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

Dictionary Entries Near femto-

femorotibial index

femto-

femtometer

See More Nearby Entries 

Cite this Entry

“Femto-.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/femto-. Accessed 31 Oct. 2024.

Copy Citation

Share

More from Merriam-Webster on femto-

Britannica.com: Encyclopedia article about femto-

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See All

How to Use Em Dashes (—), En Dashes (–) , and Hyphens (-)

Plural and Possessive Names: A Guide

The Difference Between 'i.e.' and 'e.g.'

Why is '-ed' sometimes pronounced at the end of a word?

What's the difference between 'fascism' and 'socialism'?
See All

Popular in Wordplay

See All

Weird Words for Autumn Time

What does 'at large' mean?

Terroir, Oenophile, & Magnum: Ten Words About Wine

8 Words for Lesser-Known Musical Instruments

10 Words from Taylor Swift Songs (Merriam's Version)
See All

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Word Game Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
Missing Letter A daily crossword with a twist
different halloween monsters in silhouette
A Monstrous Vocab Quiz Words That Go Bump in the Night