Energy moving in the form of particles or waves. Familiar radiations are heat,
light, radio waves, and microwaves. Ionizing radiation is a
very high-energy form of electromagnetic radiation.
US Center for Disease Control and Prevention
Glossary of Radiological Terms
Ionizing radiation is any radiation capable of displacing
electrons from atoms in the material through which it passes, thereby producing
ions. High doses of ionizing radiation may produce severe skin or tissue damage.
Examples of ionizing radiation include x-rays as well as alpha, beta and gamma
Human exposure to ionizing raditation is measured in gray (Gy), when talking
about absorbed dose, or in millisieverts (mSv), when talking about effective dos
Source: GreenFacts, based on CDC
Glossary of Radiological
Radioactivity - Ultraviolet radiation
To read about this term in context:
GreenFacts Summary on the Chernobyl Nuclear Accident: