mononucleosis

noun

mono·​nu·​cle·​o·​sis ˌmä-nə-ˌnü-klē-ˈō-səs How to pronounce mononucleosis (audio)
-ˌnyü-
: an abnormal increase of mononuclear white blood cells in the blood
specifically : infectious mononucleosis

Examples of mononucleosis 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.
Sam Darnold came down with mononucleosis before a Week 2 game in 2019. — Zack Rosenblatt, New York Times, 25 July 2025 Volantis is recovering from a bout with mononucleosis, said Schlossnagle, who added that the lefthander is still building up his strength and won’t be pitching competitively in the fall. — David Eckert, Austin American Statesman, 24 Sep. 2025 Despite dealing with mononucleosis during part of his senior season, Schultz attracted plenty of professional scouts. — Steve Lyttle, Charlotte Observer, 27 Mar. 2026 After arriving at spring training at the start of February with a persistent fever and fatigue that ultimately was diagnosed as mononucleosis, Dana threw from a mound for the first time since arriving in the desert. — Doug Padilla, Oc Register, 3 Mar. 2026 See All Example Sentences for mononucleosis

Word History

Etymology

New Latin, from International Scientific Vocabulary mononuclear + New Latin -osis

First Known Use

1902, in the meaning defined above

Time Traveler
The first known use of mononucleosis was in 1902

Phrases Containing mononucleosis

Rhymes for mononucleosis

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Browse Nearby Words

mononucleated
mononucleosis
mononucleotide
See all Nearby Words

Cite this Entry

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

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Medical Definition

mononucleosis

noun
mono·​nu·​cle·​o·​sis -ˌn(y)ü-klē-ˈō-səs How to pronounce mononucleosis (audio)
: an abnormal increase of mononuclear white blood cells in the blood
specifically : infectious mononucleosis

More from Merriam-Webster on mononucleosis

Britannica.com: Encyclopedia article about mononucleosis

Last Updated: - Updated example sentences
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