flu

IPA/fluː/
KK[flˈu]IPA/fluː/

flu — noun

1. a common viral infection that affects the respiratory system, causing a high tem

1.nounA2
Definition

a common viral infection that affects the respiratory system, causing a high temperature, body aches, and severe tiredness

Example

Tamar has been in bed with the flu all week and missed her final exams.

collocation: in bed with the flu

The doctor said everyone in the house should get a flu shot before winter.

collocation: flu shot

Common collocations
  • catch the flu
  • get the flu
  • have the flu
  • come down with the flu
  • flu season
  • flu shot
  • flu vaccine
  • flu symptoms
  • bird flu
  • swine flu
Synonyms
  • influenza

    the full medical name for the same illness; more formal than 'flu'

  • grippe

    an older, less common term for influenza; rarely used in modern English

Grammar Patterns

have/get/catch + the flu

flu + noun (as modifier)

Usage Note

Unlike most uncountable illness nouns, 'flu' is typically used with the definite article 'the' (the flu). In British English you may also hear 'have flu' without the article, but 'the flu' is common in all varieties. The informal phrase 'stomach flu' refers to a different condition involving vomiting and diarrhoea, not influenza.

Common Mistakes

I think I have a flu.
I think I have the flu.
'flu' is uncountable, so it does not take the article 'a'; use 'the' instead.
She has a cold with a fever of 39°C, so she probably has the flu.
She has a cold, which sometimes causes a mild fever, but the flu would also involve severe body aches and exhaustion.
a cold and the flu are different illnesses; the flu is more serious and causes whole-body symptoms.

Word family

Synonym discussion

Sense: noun/1

Flu and influenza refer to the same illness — influenza is the full medical name, while 'flu' is the everyday shortened form used in speech and informal writing. A cold, however, is a much milder viral infection that mainly affects the nose and throat, with symptoms like sneezing, a runny nose, and a sore throat, but rarely a high fever or severe body aches. People often say 'I have the flu' for any bad cold, but true influenza is more serious and typically involves a high temperature, exhaustion, and muscle pain throughout the body. For example: 'She thought it was just a cold, but the fever and body aches meant it was actually the flu.' 'The flu vaccine protects against influenza viruses, not the common cold.'

flu ↗influenza ↗cold ↗

Common collocations

Nouns

  • flu season
  • flu shot
  • flu vaccine
  • flu virus
  • flu symptoms
  • flu pandemic

Phrases

  • come down with the flu
  • get the flu
  • have the flu
  • catch the flu
  • be in bed with the flu

Etymology

ItalianEnglish

Flu is a shortened form of influenza, which was borrowed from Italian. In Italian, influenza means 'influence' — a reference to the medieval belief that the disease was caused by the influence of the stars. The shortened form 'flu' first appeared in written English in the 19th century.