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

An infection with Epstein-Barr virus does not necessarily cause symptoms, especially among children, though the virus is also the most common cause of mononucleosis (often referred to as mono). —Aria Bendix, NBC news, 13 Nov. 2025

Spafford, All-Orange County first team for a second year in a row last season, is recovering from mononucleosis that kept him out of summer passing activity. —Steve Fryer, Oc Register, 28 July 2025

Sam Darnold came down with mononucleosis before a Week 2 game in 2019. —Zack Rosenblatt, New York Times, 25 July 2025

Cooper recalled getting over a case of mononucleosis during her collegiate soccer stint, one of many players on the team who had been infected at the time. —Skyler Caruso, People.com, 13 June 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

• actinomycosis
• atherosclerosis
• endometriosis
• erythematosus
• erythroblastosis
• granulomatosis
• hemochromatosis
• histiocytosis
• hyperkeratosis
• ketoacidosis
• osteonecrosis
• osteoporosis

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