- The definition of a proton is a particle with a positive charge that is in the nucleus of an atom.
An example of a proton is the single proton in the nucleus of a hydrogen atom.
Origin of protonModern Latin ; from Classical Greek prōton, neuter of prōtos, first: see proto-
Origin of protonFrom Greek prōton, neuter of prōtos, first; see per1 in Indo-European roots.
From Ancient Greek πρῶτον (prōton), neuter of πρῶτος (prōtos, “first”)