at·​to·​sec·​ond | \ ˈa-(ˌ)tō-ˌse-kənd How to pronounce attosecond (audio) , -kənt \

Definition of attosecond

: one quintillionth (10−18) of a second An attosecond is to a second what a second is to the age of the universe.IEEE Spectrum

Examples of attosecond in a Sentence

Recent Examples on the Web Not a lot: a clock needs to be accurate to within a few attoseconds (10-18s) to be able to detect centimeter differences in height. Chris Lee, Ars Technica, "Portable clock provides new ruler for measuring the Earth," 13 Apr. 2020 Researchers have created light pulses lasting just 53 attoseconds using high-speed lasers. David Labrador, Scientific American, "Units of Time Stretch from Here to Eternity," 25 Jan. 2012

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'attosecond.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of attosecond

1962, in the meaning defined above

History and Etymology for attosecond

atto- + second entry 4

Keep scrolling for more

Learn More about attosecond

Time Traveler for attosecond

Time Traveler

The first known use of attosecond was in 1962

See more words from the same year

Statistics for attosecond

Cite this Entry

“Attosecond.” Dictionary, Merriam-Webster, Accessed 14 Aug. 2020.

Comments on attosecond

What made you want to look up attosecond? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

Name That Thing: Animal Edition

  • alt 5a023732e6f75
  • Name that animal:
Spell It

Can you spell these 10 commonly misspelled words?

Dictionary Devil

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

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