emission

emission — noun

1. the process by which a substance such as gas, heat, light, or radiation is sent

1.nounB2
Definition

the process by which a substance such as gas, heat, light, or radiation is sent out or released from a source

Example

The emission of heat from the engine caused the metal parts to expand.

emission of [heat/gas/light] — uncountable, general process

Felipe's research focused on the emission of light from certain chemical reactions.

Common collocations
  • emission of
  • the emission of
  • prevent the emission of
  • cause the emission of
Synonyms
  • release

    less technical; can be intentional or accidental

  • discharge

    often implies waste or unwanted substance from a specific source

  • output

    focuses on measurable quantity rather than the process itself

Antonyms
  • absorption

    the process of taking in rather than sending out

Grammar Patterns

emission of [gas/heat/light/radiation]

the emission of [substance]

Usage Note

When referring to the general process, this sense is usually uncountable (e.g., 'the emission of heat'). For a single specific instance, it can be countable (e.g., 'an emission of smoke').

Common Mistakes

The admission of gas from the pipe was dangerous.
The emission of gas from the pipe was dangerous.
'Admission' means permission to enter; 'emission' means something being sent out.

2. a specific amount of gas, especially carbon dioxide, that is produced and releas

2.nounB2
Definition

a specific amount of gas, especially carbon dioxide, that is produced and released into the air, often measured for environmental or regulatory purposes

Example

The government set strict limits on carbon emissions from cars.

countable noun: carbon emissions / CO₂ emissions

Hyun checked the factory's CO₂ emissions on the monitor every morning.

Common collocations
  • carbon emissions
  • CO₂ emissions
  • greenhouse gas emissions
  • reduce emissions
  • cut emissions
  • limit emissions
  • emissions from
Synonyms
  • output

    focuses on quantity; broader, not limited to gases

  • exhaust

    specifically waste gases from an engine or machine

Grammar Patterns

[modifier] + emissions

reduce/cut/limit + emissions

Usage Note

Almost always used in the plural form (emissions) when referring to measurable quantities. The singular (an emission) is rare outside scientific contexts.

Common Mistakes

The emission of this factory is too high.
The emissions from this factory are too high.
When referring to measured amounts, use the plural form.

3. harmful substances, especially gases or small particles, that are released into

3.nounB1
Definition

harmful substances, especially gases or small particles, that are released into the air by vehicles, factories, or power stations and damage the environment or human health

Example

The factory must clean its emissions before releasing them into the air.

countable plural: factory emissions

Diesel emissions contain tiny particles that are bad for human health.

Common collocations
  • industrial emissions
  • vehicle emissions
  • factory emissions
  • harmful emissions
  • toxic emissions
  • clean emissions
Synonyms

Grammar Patterns

industrial/vehicle/factory + emissions

emissions + contain/produce/cause

Usage Note

Frequently appears in news and political discussions about climate change and air quality. Focuses on the harmfulness of the substances, unlike sense 4 which is broader in scope.

Common Mistakes

Car emission is the main cause of air pollution.
Car emissions are the main cause of air pollution.
'Emissions' is almost always plural in this sense.

4. any solid, liquid, or gaseous substance that is released into the air from a nat

4.nounC1
Definition

any solid, liquid, or gaseous substance that is released into the air from a natural or man-made source, not necessarily harmful

Example

Volcanic emissions include ash, sulfur dioxide, and water vapor.

natural source: volcanic emissions

Dr. Nakamura sealed a sample of the chemical plant's airborne emissions in a glass jar.

Common collocations
  • volcanic emissions
  • airborne emissions
  • natural emissions
  • gaseous emissions
  • chemical emissions
Synonyms
  • release

    less technical; covers liquids and gases from any source

  • effluent

    usually refers to liquid waste, not airborne substances

Grammar Patterns

[source-type] + emissions

volcanic/natural/chemical + emissions

Usage Note

Broader than the environmental sense (sense 3). This sense includes natural emissions such as volcanic gases or plant vapours, which are not necessarily harmful. More common in scientific or technical writing.

5. a fluid or substance that an animal or human body releases, either as a normal p

5.nounC1
Definition

a fluid or substance that an animal or human body releases, either as a normal process or as a sign of illness

Example

The patient's nasal emissions were tested for signs of infection.

medical register: nasal emissions

The doctor checked the bodily emissions for signs of a stomach problem.

Common collocations
  • nasal emissions
  • bodily emissions
  • ocular emissions
  • the emission of [fluid]
Synonyms
  • discharge

    more common in medical contexts; less formal

  • secretion

    specifically refers to substances produced by glands

Grammar Patterns

[body-part] + emissions

nasal/ocular/intestinal + emissions

Usage Note

Very formal or medical register. In everyday conversation, words like 'discharge' or 'waste' are far more common. Typically used by doctors in clinical reports.

Common Mistakes

I have a lot of emission from my nose.
I have a lot of nasal discharge.
'Emission' sounds overly technical in everyday speech about the body.

Word family

  • emit
    verbB2
  • emitter
    nounC1
  • emissive
    adjectiveC1
  • emissivity
    nounC2

Synonym discussion

Sense: noun/2

Emission, discharge, and release all describe something being sent out, but they differ in context and formality. Emission is the most formal term and is used almost exclusively for gases or radiation from technical, industrial, or environmental sources — you see it in climate reports and scientific papers. Discharge often implies waste or unwanted fluid from a specific source, such as a factory pipe or a wound, and can apply to both gases and liquids. Release is broader in scope and less technical: any substance set free, whether intentional or accidental, can be a release. Exhaust refers specifically to waste gases from an engine or machine. Pollution is the effect these substances have on the environment, not the act of sending them out. For example: a car's carbon emissions are measured in tonnes; toxic waste was discharged into the river; the accidental release of gas forced a neighbourhood evacuation; diesel exhaust contains fine particles that harm the lungs.

discharge ↗release ↗exhaust ↗pollution ↗

Common collocations

Nouns

Adverbs

Phrases

  • cut emissions by
  • reduce emissions to
  • limit emissions from

Prepositions

Etymology

LatinFrenchEnglish

Emission comes from the Latin word 'emittere', formed from 'e-' (meaning 'out') and 'mittere' (meaning 'to send'). Originally used in English for sending out physical substances, it later expanded to cover radiation, light, sound, and environmental pollutants.