radiation

radiation — noun

1. harmful energy in the form of rays or particles that is released by radioactive

1.nounB2
Definition

harmful energy in the form of rays or particles that is released by radioactive substances and can damage living cells or cause illness

Example

Minho checked his dosimeter for radiation exposure every day at the storage facility.

collocation: radiation exposure

Kwame's doctor explained that high doses of radiation can increase the risk of cancer.

collocation: doses of radiation

Common collocations
  • radiation leak
  • radiation poisoning
  • radiation sickness
  • nuclear radiation
  • harmful radiation
  • background radiation
Synonyms
  • radioactivity

    refers to the property or process of a substance emitting radiation, not the radiation itself — a material has radioactivity

  • fallout

    specifically the radioactive particles that fall to the ground after a nuclear explosion

  • contamination

    means radioactive material has spread to an area or object — distinct from the energy waves themselves

Grammar Patterns

radiation + from + [source]

[high/low/dangerous] levels of radiation

exposure to radiation

Usage Note

Commonly uncountable. Frequently used with modifiers that indicate the amount or danger: 'high levels of', 'dangerous', 'harmful', 'low-dose'. The source is typically a radioactive substance, nuclear reactor, or nuclear accident. Distinguished from sense 2 by the implication of danger and the nuclear/radioactive origin.

Common Mistakes

The sun sends nuclear radiation to the earth.
The sun sends thermal radiation to the earth.
Nuclear radiation comes specifically from radioactive materials and nuclear reactions, not from the sun's normal fusion process.
I bought a device that removes radiation from the room.
I bought a device that measures radiation levels in the room.
Radiation cannot be physically removed or filtered from air like dust or gas.

2. energy that moves as electromagnetic waves — including sunlight, heat from a fir

2.nounB2
Definition

energy that moves as electromagnetic waves — including sunlight, heat from a fire, and radio signals — through air, empty space, or solid materials

Example

Alessia could feel the sun's radiation warming her skin even on a cold winter morning.

solar radiation / heat transfer

Joshua learned in science class that infrared radiation is invisible to the human eye.

infrared radiation — invisible electromagnetic waves

Common collocations
  • solar radiation
  • thermal radiation
  • infrared radiation
  • ultraviolet radiation
  • microwave radiation
  • background radiation
Synonyms
  • electromagnetic waves

    more technical term for the same phenomenon, covering the entire spectrum from radio to gamma rays

  • thermal emission

    specifically refers to heat radiation from warm objects, a subset of this sense

  • radiant energy

    formal physics term for energy carried by electromagnetic waves

Grammar Patterns

[type] + radiation

radiation + from + [source]

Usage Note

Used in both scientific and everyday contexts. The type of radiation is often specified by a modifier: 'solar radiation', 'thermal radiation', 'ultraviolet radiation', 'microwave radiation'. Unlike sense 1, this meaning is not inherently dangerous — it simply describes how energy moves. Many types (visible light, radio waves) are harmless.

Common Mistakes

Microwaves are a type of nuclear radiation.
Microwaves are a type of electromagnetic radiation.
Microwaves are non-ionising radiation, which is completely different from nuclear/radioactive radiation.

3. the use of controlled radioactive rays, delivered by a machine or implanted mate

3.nounB2
Definition

the use of controlled radioactive rays, delivered by a machine or implanted material, to destroy cancer cells or shrink tumours as part of medical care

Example

Mira went to the hospital for radiation three times a week to treat her tumour.

collocation: go for radiation / receive radiation

The doctors used targeted radiation to destroy the cancer cells without harming healthy tissue.

collocation: targeted radiation / radiation treatment

Common collocations
  • radiation therapy
  • radiation treatment
  • radiation oncologist
  • radiation dose
  • radiation session
  • targeted radiation
  • palliative radiation
Synonyms
  • radiotherapy

    the formal medical term for radiation treatment, used interchangeably in clinical contexts

  • radiation therapy

    the full compound noun; more common in patient-facing communication

  • irradiation

    technical term for exposing tissue to radiation, but rarely used in patient contexts

Antonyms
  • chemotherapy

    uses drugs rather than radiation to treat cancer

Grammar Patterns

radiation + therapy / treatment

undergo / receive / have radiation

[number] + rounds / sessions of radiation

Usage Note

Often shortened to 'radiotherapy'. The full forms 'radiation therapy' and 'radiation treatment' are common in patient-facing contexts. Patients typically receive radiation in daily sessions over several weeks. This sense is always planned and controlled — distinguished from sense 1, where radiation is accidental and dangerous.

Common Mistakes

The doctor gave me a radiation medicine to take at home.
The doctor recommended radiation therapy at the hospital three times a week.
Radiation is not a pill or liquid medicine; it is a treatment delivered by a machine in a clinical setting.
Idioms

radiation therapy

idiom

a medical treatment that uses controlled doses of radiation to destroy cancer cells or reduce the size of tumours

After her surgery, the doctor recommended six weeks of radiation therapy to remove any remaining cancer cells.

Radiation therapy is often combined with chemotherapy for more aggressive types of cancer.

radiation sickness

idiom

an illness caused by exposure to very high levels of radiation, with symptoms such as nausea, weakness, and loss of hair

Workers who entered the reactor building without protection developed radiation sickness within hours.

The first sign of radiation sickness is often a sudden feeling of nausea and extreme tiredness.

radiation exposure

idiom

the state of being subjected to radiation, either from natural sources or from human activities such as medical scans or nuclear accidents

People who live near the closed plant are concerned about long-term radiation exposure from contaminated groundwater.

A single chest X-ray involves very low radiation exposure, roughly equal to ten days of natural background radiation.

Word family

Synonym discussion

Sense: noun/1

Radiation (sense 1) refers to the harmful energy waves or particles that radioactive substances emit — it is the energy itself. Radioactivity is the property or process of a substance releasing that energy; you would say 'this material has high radioactivity' but 'the material gives off dangerous radiation'. Contamination is the unwanted presence of radioactive material in a place or on an object — the ground can be contaminated with radioactive dust, but the dust itself emits radiation. Fallout specifically describes the radioactive particles that drift down from the sky after a nuclear explosion or reactor accident. For example: 'After the accident, monitors detected radiation in the air (the energy waves), checked the radioactivity level of the soil (the property), declared the water supply contaminated (unwanted radioactive material), and warned about fallout from the blast (falling particles).'

radiation ↗radioactivitycontaminationfallout ↗

Common collocations

Nouns

Adverbs

Phrases

  • radiation from [source]
  • level of radiation
  • exposure to radiation
  • protection against radiation
  • dose of radiation

Prepositions

Etymology

LatinFrenchEnglish

Derived from the Latin word 'radiatio', meaning 'a shining or beaming', which came from the verb 'radiare' ('to emit rays') and the noun 'radius' ('ray' or 'spoke of a wheel'). The term entered English in the mid-16th century with the general sense of 'emission of rays'. Its modern scientific usage began in the late 19th century, following Wilhelm Röntgen's discovery of X-rays in 1895 and Henri Becquerel's discovery of radioactivity in 1896.