In science, a cation is an ion, or charged particle, with a positive charge. In other words, a cation has more protons than electrons.

If you come across the word ion in a chemistry or physics class, cation and anion won't be far behind. An ion is a particle that has an electrical charge. When an ion's charge is negative, it's more specifically called an anion, and when it's positive, you can use the term cation. The Greek source is kation, which means "going down."

Definitions of cation
  1. noun
    a positively charged ion
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    hydrogen ion
    a positively charged atom of hydrogen; that is to say, a normal hydrogen atomic nucleus
    the univalent cation R-N:N- (where R is an aromatic hydrocarbon); found in salts that are used in manufacturing azo dyes
    type of:
    a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
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