- Emission or propagation of electromagnetic energy (waves/rays), or the waves/rays themselves; a stream of electromagnetic particles (electrons, neutrons, protons, alpha particles) or a mixture of these. The most common source is the sun.
Definition from: MeSH via Unified Medical Language System at the National Library of Medicine
- Energy released in the form of particles or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, and medical x-rays.
Definition from: Physician Data Query via Unified Medical Language System at the National Library of Medicine
Related discussion in the Handbook
See also Understanding Medical Terminology.