flu
- 1A contagious illness caused by the influenza virus, bringing fever, muscle aches, fatigue, and respiratory symptoms.
She caught the flu and stayed home from work all week.
Every winter, the flu spreads quickly through crowded schools and offices.
Similarinfluenza
Note
Everyday English cut influenza down to the short syllable inside it, and the clipped form carries the full meaning. It usually behaves as an uncountable noun and is easy about the article: you catch flu or catch the flu, get over the flu, transmit flu, with no change in sense. The plural flus is available for when the illness is counted.
- 2A short-lived stomach and intestinal illness causing nausea, vomiting, and diarrhea, despite not actually being caused by the influenza virus.
The whole family came down with the flu after the picnic, and everyone was throwing up by midnight.
I couldn't keep anything down for two days with that flu going around the office.
Similarbug, gastroenteritis
Note
A second shortening: here the word stands in for stomach flu, dropping the very word that told the two illnesses apart. It belongs to casual talk. Because it shares its name with the influenza meaning, context and symptoms do the disambiguating. When the difference matters, as in speaking to a doctor or writing for strangers, say stomach flu in full.
Practice
Can you tell the meanings of flu apart? Answer 2 quick questions from this page, or write your own sentence and AI will check it.
Origin
A shortened form of "influenza."