Definition of Neutron
an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus
A neutral hadron that is stable in the atomic nucleus but decays into a protron, an electron and an antineutrino with a mean life of 12 minutes outside the nucleus. Neutrons exist in all atomic nuclei except normal hydrogen. Reported in 1932 by James Chadwick.