Definition of fermi in English:


Syllabification: fer·mi
Pronunciation: /ˈfermē, ˈfər-

noun (plural same)

  • A unit of length equal to 10−15 meter (one femtometer), used in nuclear physics. It is similar to the diameter of a proton.
    More example sentences
    • 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.
    • 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.
    • 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).

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