Meaning & use
femtometer
Last updated
A unit of length equal to one quadrillionth (10⁻¹⁵) of a meter, used mainly to measure subatomic distances.
See it in a sentence
The radius of a proton is roughly one femtometer.
Nuclear physicists measure distances between particles in femtometers.
A note on using this word
Also called a "fermi," after physicist Enrico Fermi, this unit is essential in nuclear and particle physics, where ordinary units like meters are far too large.
Words with a similar meaning
fermi
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