cytosine

noun

cy·​to·​sine ˈsī-tə-ˌsēn How to pronounce cytosine (audio)
: a pyrimidine base C4H5N3O that codes genetic information in the polynucleotide chain of DNA or RNA compare adenine, guanine, thymine, uracil

Examples of cytosine 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.
Adenine always pairs with thymine, and guanine always pairs with cytosine. — IEEE Spectrum, 2 Oct. 2025 Those rungs are made up of pairs of four different chemical building blocks, called bases — adenine, thymine, cytosine and guanine (A,T,C and G). — F.d. Flam, Mercury News, 26 Nov. 2025 The system used here involves a protein that chemically lops off a nitrogen from the base cytosine (C), converting it to something that base-pairs more like thymidine (T). — ArsTechnica, 9 Apr. 2026 Biology’s four bases—adenine (A), thymine (T), cytosine (C) and guanine (G)—encode the instructions that keep life alive. — Andrew Whalen, Forbes.com, 9 July 2025 See All Example Sentences for cytosine

Word History

Etymology

International Scientific Vocabulary cyt- + -ose + -ine entry 2

First Known Use

1894, in the meaning defined above

Time Traveler
The first known use of cytosine was in 1894

Rhymes for cytosine

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Browse Nearby Words

cytoreticulum
cytosine
cytoskeletal
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Cite this Entry

“Cytosine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cytosine. Accessed 8 Jul. 2026.

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Kids Definition

cytosine

noun
cy·​to·​sine ˈsīt-ə-ˌsēn How to pronounce cytosine (audio)
: a chemical base that is a pyrimidine and codes genetic information in DNA and RNA compare adenine, guanine, thymine, uracil

Medical Definition

cytosine

noun
cy·​to·​sine ˈsīt-ə-ˌsēn How to pronounce cytosine (audio)
: a pyrimidine base C4H5N3O that codes genetic information in the polynucleotide chain of DNA or RNA compare adenine, guanine, thymine, uracil

More from Merriam-Webster on cytosine

Britannica.com: Encyclopedia article about cytosine

Last Updated: - Updated example sentences
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