# mono

/ˈmoʊnoʊ/ (US) · /mˈɒnəʊ/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/mono
Updated: 2026-08-15

## Definition

an illness that makes you feel very tired and gives you a sore throat for a long time. It is common among teenagers and young adults and spreads through saliva.

For teachers: an infectious disease caused by the Epstein-Barr virus, characterised by extreme fatigue, fever, and swollen lymph nodes. Informal in register; the full medical term is infectious mononucleosis.

## Examples

- He missed two weeks of school because he had mono.
- After feeling exhausted for a month, the student went to the clinic and tested positive for mono.
- While mono is rarely dangerous for healthy individuals, the resulting fatigue can linger for months, significantly impacting a student's academic performance and social life during the recovery period.

## Pitfalls

- Not "He has a mono" but "He has mono" — Unlike 'a cold' or 'a headache', mono is treated as an uncountable disease name and does not take an indefinite article.

## Usage notes

- Typically used without an article ('he has mono') or with the definite article in specific contexts ('the mono she caught').

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.