femtometer
noun
fem·to·me·ter
ˈfem(p)-tə-ˌmē-tər 
-tō-
: a unit of length equal to 10−15 meters : one quadrillionth of a meter
Examples of femtometer in a Sentence
Recent Examples on the Web
This explains why the proton and neutron have particular sizes to them, where each one has a radius that’s a little smaller than a femtometer.
—
Ethan Siegel, Forbes, 20 Apr. 2021
Pohl and his team were surprised to find a lower value for the radius, pegging it at 0.84 femtometer—well outside the range of potential sizes established by earlier measurements.
—Dan Falk, Scientific American, 28 Nov. 2019
Finally, the results are in: Hessels and company have pegged the proton’s radius at 0.833 femtometers, give or take 0.01, a measurement exactly consistent with Pohl’s value.
—Quanta Magazine, 11 Sep. 2019
The result: their measurement of 0.833 femtometers (just under one-trillionth of a meter) agrees with the smaller value from the 2010 study.
—Jennifer Ouellette, Ars Technica, 5 Sep. 2019
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Ethan Siegel, Forbes, 20 Apr. 2021
Pohl and his team were surprised to find a lower value for the radius, pegging it at 0.84 femtometer—well outside the range of potential sizes established by earlier measurements.
—Dan Falk, Scientific American, 28 Nov. 2019
Finally, the results are in: Hessels and company have pegged the proton’s radius at 0.833 femtometers, give or take 0.01, a measurement exactly consistent with Pohl’s value.
—Quanta Magazine, 11 Sep. 2019
The result: their measurement of 0.833 femtometers (just under one-trillionth of a meter) agrees with the smaller value from the 2010 study.
—Jennifer Ouellette, Ars Technica, 5 Sep. 2019
Cite this Entry
“Femtometer.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/femtometer. Accessed 9 Sep. 2025.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
Share