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
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
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
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
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Ethan Siegel, Forbes, 20 Apr. 2021
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
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
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 30 Jun. 2025.
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