An Etymological Dictionary of Astronomy and Astrophysics

An unstable elementary particles, belonging to the class called → baryons, which have greater mass than the neutron but very short lives (10^-8 to 10^-10 seconds).

See also: From → hyper- + → -on
a suffix used in the names of elementary particles (gluon; meson; neutron; graviton, and so on).