carbon dioxide

noun

: a heavy colorless gas CO2 that does not support combustion, dissolves in water to form carbonic acid, is formed especially in animal respiration and in the decay or combustion of animal and vegetable matter, is absorbed from the air by plants in photosynthesis, and is used in the carbonation of beverages

Examples of carbon dioxide in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Once operational, the system is expected to prevent approximately 5,000 tons of carbon dioxide emissions each year. — Atharva Gosavi, Interesting Engineering, 26 Aug. 2026 In a new study, scientists estimate the role of carbon dioxide emissions from more than 100 of the world’s largest fossil fuel companies. — Ian James, Los Angeles Times, 26 Aug. 2026 Because carbon dioxide can remain in the atmosphere for hundreds of years, and so much has already built up, the damage could take centuries to reverse. — Peter Prengaman, Fortune, 24 Aug. 2026 For years, most machines that pull carbon dioxide out of ambient air, known as direct air capture (DAC) systems, have relied on steam for heat. — Emily Waltz, IEEE Spectrum, 19 Aug. 2026 See All Example Sentences for carbon dioxide

Word History

First Known Use

1867, in the meaning defined above

Time Traveler
The first known use of carbon dioxide was in 1867

Rhymes for carbon dioxide

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Browse Nearby Words

carbon dichloride
carbon dioxide
carbon disulfide
See all Nearby Words

Cite this Entry

“Carbon dioxide.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/carbon%20dioxide. Accessed 1 Sep. 2026.

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Kids Definition

carbon dioxide

noun
: a heavy colorless gas CO2 that is formed especially by the burning and breaking down of organic substances (as in animal respiration), is absorbed from the air by plants in photosynthesis, and has many industrial uses

Medical Definition

carbon dioxide

noun
: a heavy colorless gas CO2 that does not support combustion, dissolves in water to form carbonic acid, is formed especially in animal respiration and in the decay or combustion of animal and vegetable matter, is absorbed from the air by plants in photosynthesis, and is used in the carbonation of beverages

More from Merriam-Webster on carbon dioxide

Britannica.com: Encyclopedia article about carbon dioxide

Last Updated: - Updated example sentences
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