mononucleosis

noun

mono·​nu·​cle·​o·​sis ˌmä-nə-ˌnü-klē-ˈō-səs 

-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

Almost everyone is infected with this virus, which can cause mononucleosis, and a very small fraction of those infected will one day develop cancer. — Adam Cohen, Oklahoman, 18 Aug. 2026

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

These triggers are usually associated with a gradual onset of CFS, but sudden onset can be caused by certain infections, with two classic ones being COVID and mononucleosis, past research has shown. — Shiv Sudhakar, FOXNews.com, 20 Dec. 2025

Word History

Etymology

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

First Known Use

1902, in the meaning defined above

Phrases Containing mononucleosis

• infectious mononucleosis

Rhymes for mononucleosis

• amyloidosis
• anaplasmosis
• anastomosis
• aponeurosis
• apotheosis
• aspergillosis
• blastomycosis
• coccidiosis
• cryptococcosis
• cysticercosis
• endocytosis
• exocytosis

Medical Definition

mononucleosis

noun

mono·​nu·​cle·​o·​sis -ˌn(y)ü-klē-ˈō-səs 

: an abnormal increase of mononuclear white blood cells in the blood

specifically : infectious mononucleosis