Definition of proton in English:



  • A stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron.

    • ‘Overall, atoms are neutral and the number of protons in their nuclei equals the number of electrons.’
    • ‘The matter was composed primarily of an ionized gas of electrons, protons, and helium nuclei.’
    • ‘An alpha particle consists of two protons and two neutrons; it is the nucleus of a helium atom.’
    • ‘The strong force also attracts protons to protons or neutrons to neutrons.’
    • ‘Its atoms have a nucleus of two protons and two neutrons, orbited by two electrons.’

The mass of the proton is 1,836 times greater than that of the electron. The atoms of each chemical element have a characteristic number of protons in the nucleus; this is known as the atomic number. The common isotope of hydrogen has a nucleus consisting of a single proton


1920s from Greek, neuter of prōtos ‘first’.