carbon dioxide

Meanings

1. 1noununcountable

   A colorless, odorless gas that animals breathe out and plants use to make food, and that also comes from burning fuels.

   Grammar: Uncountable, so no plural and no 'a' before it: 'Carbon dioxide is a gas.'

   Patterns

   • carbon dioxide emissions
   • levels of carbon dioxide
   • absorb carbon dioxide

   Plants take in carbon dioxide from the air and release oxygen.

   Cars and factories produce large amounts of carbon dioxide.

   Scientists measure carbon dioxide levels in the atmosphere.

2. 2noununcountablechemistry

   The gas with the chemical formula CO2, used in fizzy drinks, fire extinguishers, and some industrial processes.

   Grammar: Still uncountable when referring to the substance in products or equipment.

   Patterns

   • carbon dioxide in drinks
   • carbon dioxide fire extinguisher

   The bubbles in soda water are carbon dioxide.

   A carbon dioxide fire extinguisher can put out electrical fires.

Common combinations

carbon dioxide emissions

Many countries are trying to reduce carbon dioxide emissions.

carbon dioxide levels

Higher carbon dioxide levels can affect plant growth.

absorb carbon dioxide

Trees absorb carbon dioxide and store carbon.

produce carbon dioxide

When you burn wood, it produces carbon dioxide and water vapor.

Synonyms and how they differ

CO2

The chemical formula, used mainly in scientific or technical writing; it is not a synonym in everyday speech.

Word family

carbon noun

The chemical element that carbon dioxide contains.

dioxide noun

A compound with two oxygen atoms, as in carbon dioxide.

Commonly confused: carbon dioxide or carbon monoxide?

Practice

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