The emissions of the most common forms of spontaneous radioactive decay are the alpha (α) particle, the beta (β) particle, the gamma (γ) ray, and the neutrino.
Answer: Alpha, beta, and gamma after the first three letters of the Greek alphabet. Alpha and beta particles consist of matter, and gamma rays are bursts of energy. The type of radiation emitted depends on the radioactive substance; cesium-137, for example, produces beta and gamma radiation but not alpha particles.