(β particle).A charged particle emitted from a radioactive atomic nucleus either natural or manufactured. The energies of β particles range from 0 to 4 MeV. They carry a single charge; if this is negative, the particle is identical with an electron; if positive, it is a positron. β-rays (streams of these particles) may cause skin burns and are harmful within the body. Protection to the skin can be afforded by a thin sheet of metal.See Electron; Decay; Radioactivity.