Definition of fermi in English:



  • A unit of length equal to 10⁻¹⁵ metre (one femtometre), used in nuclear physics. It is similar to the diameter of a proton.

    • ‘About half a century later, Robert Hofstadter won the 1961 Nobel Prize in physics for his work verifying that the radius of an atomic nucleus is about one fermi.’
    • ‘In order to fuse two hydrogen nuclei together, though, we must force another proton into the hydrogen atom within a distance of 1 fermi from the atom's proton.’
    • ‘It acts between two neutrons, between two protons, or between a neutron and a proton, as long as they are no farther apart than a distance of one fermi.’


Early 20th century: named after E. Fermi (see Fermi, Enrico).