Radiation may have one of the following meanings.
- Radiation (in physics), an emission of energy or particles.
- Radiation in evolutionary biology:
- Evolutionary radiation (to which Radiation (biology) redirects), a diversification into several lineages from a common ancestor, and
- Adaptive radiation, an evolutionary radiation to fill many ecological niches. Often especially rapid, produces a wide range of apomorphies, and is commonly found when new habitat such as on oceanic archipelagos is colonized.
- Radiation (medicine), characteristics of e.g. pain to spread to other parts of the body than the origin.
