# radiation

/ˌɹeɪdiˈeɪʃən/ (US) · /ɹˌeɪdɪˈeɪʃən/ (UK)

Source: https://englishreference.com/word/radiation
Updated: 2026-06-19

## Senses

### 1. energy waves or particles

noun · CEFR B2

energy that moves through the air or space, like heat from a fire or light from the sun.

For teachers: the process in which energy is emitted as particles or waves, including electromagnetic radiation such as light and radio waves.

- The sun's radiation provides the heat and light that plants need to grow.
- Thermal radiation allows heat to be transferred across a vacuum, which is why we can feel the warmth of the sun despite the empty space between us.

### 2. radioactive energy

noun · CEFR B2

dangerous energy produced by nuclear materials or X-ray machines.

For teachers: ionising radiation emitted by radioactive substances or high-energy equipment, often associated with health risks or medical treatments.

- The workers wore special suits to protect themselves from radiation at the power plant.
- The patient underwent a course of targeted radiation to shrink the tumour before the surgical team attempted to remove it.

Usage: Often used as an uncountable noun when referring to the general phenomenon of radioactivity.

### 3. evolutionary diversification

noun · CEFR C2 · Academic · Technical

the process where one type of animal or plant quickly develops into many new species.

For teachers: the rapid diversification of a lineage into several new forms that fill different ecological niches.

- The radiation of finches on the islands led to many different beak shapes.
- The fossil record provides clear evidence of a massive mammalian radiation following the extinction of the dinosaurs at the end of the Cretaceous period.

Usage: Commonly appears in the phrase 'adaptive radiation'.

## Examples

- The sun sends out radiation that can burn your skin.
- Doctors use lead aprons to protect themselves from radiation when they take X-ray images of patients.
- While low levels of background radiation are naturally present in the environment, prolonged exposure to high-energy ionising sources can cause significant damage to living tissue and DNA.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.