virus
VEYE-ruhs
Virus (noun) means a microscopic infectious agent that can only reproduce inside a living host cell, sometimes causing disease. Example: “The flu virus mutates constantly, which is why new vaccines are needed every year.”
noun
1
A microscopic infectious agent that can only reproduce inside a living host cell, sometimes causing disease.
"The flu virus mutates constantly, which is why new vaccines are needed every year."
"Scientists study how a virus enters a cell and copies itself."
"A virus is too small to be seen without a powerful microscope."
2
A disease caused by such an agent.
"He was out sick with some kind of stomach virus all week."
"Half the class stayed home last week with a nasty virus."
"Rest and plenty of fluids are the best cure for a mild virus."
3
Malicious software that spreads between computers, often damaging files or data.
"Her laptop got a virus after she opened an email attachment."
"The antivirus program found a virus hidden inside the downloaded file."
"Our office network was down for hours after a virus spread through it."
How to use virus
Learner’s notesIn plain EnglishA germ that causes disease, or, separately, malicious computer software that spreads and causes harm.
Easily confused with
Common pairings
catch a virus
a computer virus
a virus outbreak
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Word forms
- Plural
- viruses, virusses, vira, viri, virii
- Third person singular
- viruses
- Past tense
- virused
Fill the gap
Can you complete this real example?
The flu _____ mutates constantly, which is why new vaccines are needed every year.
Etymology
From Latin virus, meaning "poison" or "slimy liquid." The computer sense was popularized after appearing in David Gerrold's 1972 novel When HARLIE Was One.
Class of 1972
virus joined the language around 1972.
See the full Class of 1972 →
Synonyms
View more →Related words
Rhymes for virus
See all rhymes for virus →Frequently asked questions
What does “virus” mean?
The word “virus” means a microscopic infectious agent that can only reproduce inside a living host cell, sometimes causing disease. In plain terms, a germ that causes disease, or, separately, malicious computer software that spreads and causes harm.
How do you pronounce “virus”?
“Virus” is pronounced VEYE-ruhs (/ˈvaɪ.ɹəs/ in IPA).
How do you use “virus” in a sentence?
Here is “virus” used in a sentence: “The flu virus mutates constantly, which is why new vaccines are needed every year.”
What part of speech is “virus”?
“Virus” is a noun.
Where does the word “virus” come from?
The word “virus” dates back to around 1972 and comes from Latin. From Latin virus, meaning "poison" or "slimy liquid." The computer sense was popularized after appearing in David Gerrold's 1972 novel When HARLIE Was One.
Is “virus” a common word?
“Virus” is a fairly common word in modern English, usually learned at around the B1 level.
How many meanings does “virus” have?
“Virus” has 3 distinct senses listed in this dictionary. The most common is: a microscopic infectious agent that can only reproduce inside a living host cell, sometimes causing disease.
What is the difference between a virus and a bacterium?
Bacteria are living, single-celled organisms that can grow and reproduce on their own. A virus is far smaller and is not fully alive — it can only replicate by hijacking a living host cell. Crucially, antibiotics work against bacteria but have no effect whatsoever on viruses.
Are viruses alive?
Scientists debate this. Viruses carry genetic material and can evolve, but they cannot grow, produce energy, or reproduce by themselves — they must invade a host cell to make copies. Because they lack the machinery of life on their own, many biologists place them on the boundary between living and non-living.
Can a virus be cured with antibiotics?
No. Antibiotics target bacteria and do nothing to viruses. Most viral infections are fought off by the body's own immune system, sometimes helped by antiviral medicines or prevented by vaccines. Taking antibiotics for a virus is ineffective and fuels antibiotic resistance, which is why doctors avoid prescribing them for it.
What are some diseases caused by viruses?
Viruses cause many familiar illnesses, including the common cold, influenza (flu), COVID-19, measles, chickenpox, and HIV. Some viral infections are mild and pass quickly, while others are serious or lifelong. Vaccines exist to prevent many of them, which is why immunisation programmes so often target viral diseases.
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