flu

The word “flu” means a common contagious viral illness causing fever, aches, and fatigue; short for influenza. In plain terms, a common, unpleasant viral illness that spreads especially in the colder months.

“Flu” is pronounced floo (/fluː/ in IPA).

Here is “flu” used in a sentence: “Half the office called in sick with the flu last week.”

“Flu” is a noun.

The word “flu” comes from Italian. A shortened form of "influenza," itself borrowed from Italian.

“Flu” is a fairly common word in modern English, usually learned at around the B1 level.

The flu, short for influenza, is a contagious viral illness that typically brings fever, body aches, and fatigue, and it tends to hit harder and faster than a cold. A common cold usually causes milder symptoms such as a runny nose and sore throat.

Despite the nickname "stomach flu," the flu (influenza) is mainly a respiratory illness marked by fever, aches, and fatigue rather than a stomach illness. A stomach bug that causes vomiting and diarrhoea is usually a different kind of infection.

Both are correct. American English commonly says "the flu" ("I have the flu"), while British English often drops the article and says "flu" ("I've got flu").

Modern English writes it simply as flu, with no apostrophe, even though it is shortened from influenza. The older form with a leading apostrophe, 'flu, now looks dated.