carbon dioxide

American  

[kahr-buhn dahy-ok-sahyd] / ˈkɑr bən daɪˈɒk saɪd /

noun

1. a colorless, odorless, incombustible gas, CO 2 , present in the atmosphere and formed during respiration, usually obtained from coal, coke, or natural gas by combustion, from carbohydrates by fermentation, by reaction of acid with limestone or other carbonates, or naturally from springs: used extensively in industry as dry ice, or carbon dioxide snow, in carbonated beverages, fire extinguishers, etc.

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carbon dioxide British  

noun

1. Also called: carbonic-acid gas.  a colourless odourless incombustible gas present in the atmosphere and formed during respiration, the decomposition and combustion of organic compounds, and in the reaction of acids with carbonates: used in carbonated drinks, fire extinguishers, and as dry ice for refrigeration. Formula: CO 2

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carbon dioxide Scientific  

1. A colorless, odorless gas that is present in the atmosphere and is formed when any fuel containing carbon is burned. It is breathed out of an animal's lungs during respiration, is produced by the decay of organic matter, and is used by plants in photosynthesis. Carbon dioxide is also used in refrigeration, fire extinguishers, and carbonated drinks. Chemical formula: CO ₂ .

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carbon dioxide Cultural  

1. A compound made up of molecules containing one carbon atom and two oxygen atoms.

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Discover More

Carbon dioxide is normally found as a gas that is breathed out by animals and absorbed by green plants. The plants, in turn, return oxygen to the atmosphere. (See carbon cycle and respiration.)

Carbon dioxide is also given off in the burning of fossil fuels (see greenhouse effect).

Etymology

Origin of carbon dioxide

First recorded in 1870–75

Compare meaning

How does carbon-dioxide compare to similar and commonly confused words? Explore the most common comparisons:

• carbon monoxide vs. carbon dioxide

Example Sentences

It pumped out nearly 20 million tonnes of planet-heating carbon dioxide in 2022, making it the world's highest-emitting oil refinery, according to non-profit Climate Trace.

From Barron's • May 28, 2026

The UK has a legally-binding commitment to reach that point by 2050 while in Scotland, which has more available land for planting trees to absorb carbon dioxide, the target date is 2045.

From BBC • May 26, 2026

HFCs are known as “super pollutants” because their impacts on climate change can be hundreds of thousands of times greater than carbon dioxide during their shorter lifespans.

From Los Angeles Times • May 21, 2026

It absorbs a huge amount of the heat trapped by greenhouse gases, along with a significant share of the carbon dioxide produced by human activity.

From Science Daily • May 14, 2026

As always, the dangerous part about life support is managing carbon dioxide.

From "The Martian" by Andy Weir