: any of a large group of submicroscopic infectious agents that are usually regarded as nonliving extremely complex molecules, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, and plants
: a computer program that is usually disguised as an innocuous program or file, that often produces copies of itself and inserts them into other programs, and that when run usually performs a malicious action (such as destroying data or damaging software)
Is the illness caused by bacteria or a virus?
I think I have the virus that's going around this winter.
The software checks your hard drive for viruses.
Recent Examples on the WebBut that’s not the case for infants and toddlers, who are at higher risk of the virus becoming severe or life-threatening.—Karen Garcia, Los Angeles Times, 22 Nov. 2023 For the majority of those aged 6 months and older, the CDC recommends receiving the standard quadrivalent flu vaccine, which protects against four different strains of the virus.—Mary Kekatos, ABC News, 22 Nov. 2023 The coffee prevented entry of the SARS-CoV-2 infection by keeping the virus from entering host cells.—Melissa Rudy, Fox News, 21 Nov. 2023 How to get the new COVID vaccine for free, with or without insurance
The new test kits comes as health authorities have been closely scrutinizing data tracking the virus, with cases forecast to increase this winter.—Alexander Tin, CBS News, 20 Nov. 2023 However, cold weather can contribute to conditions that facilitate the spread of viruses.—Katie Liu, Discover Magazine, 16 Nov. 2023 Chickenpox is a highly contagious virus that causes a blistering rash.—Parents Editors, Parents, 14 Nov. 2023 In the event of an invasion from pathogens like viruses or bacteria, cGAS identifies foreign DNA, working in alliance with STING to initiate defensive measures.—William A. Haseltine, Forbes, 13 Nov. 2023 But the virus quickly spread among children left unprotected.—Erika Edwards, NBC News, 9 Nov. 2023 See More
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'virus.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Middle English, "pus, discharge from a sore, semen," borrowed from Latin vīrus (neuter) "venom, poisonous fluid, acrid element in a substance, secretion with medical or magical properties," going back to an Indo-European base *u̯is-/*u̯īs- "poison, venom," whence also Middle Irish fí "venom, poison, evil," Greek īós "poison," Tocharian A wäs and Tocharian B wase, Sanskrit viṣáṃ, Avestan viš, viša- (also vīš?); (sense 1) borrowed from German, borrowed from Latin
The application of Latin vīrus to the submicroscopic infectious agents now considered viruses (rather than to any infectious agent) was apparently first made by the Dutch microbiologist Martinus Beijerinck (1851-1931) in "Ueber ein Contagium vivum fluidum als Ursache der Fleckenkrankheit der Tabaksblätter," Verhandelingen der Koninklijke Akademie van Wetenschappen te Amsterdam, Tweede Sectie, Deel VI, no. 5 (1898). Beijerinck, in studying tobacco mosaic virus, mistakenly believed that the agent was a fluid (contagium vivum fluidum, "living fluid infection") because it passed through filters capable of trapping bacteria. — The neuter gender of vīrus suggests that it was originally an s-stem; forms in text other than the nominative and accusative are perhaps found only in Lucretius. The length of the vowel in Latin, Irish, and Greek, in contrast to the short vowel in Tocharian and Indo-Iranian, has been variously accounted for. M. Mayrhofer (Etymologisches Wörterbuch des Altindoarischen) suggests that the etymon was originally a root noun, *u̯īs, *u̯is-ó-, with lengthening of the monosyllabic vowel; the daughter languages then generalized one or the other form.
: any of a large group of very tiny infectious agents that are too small to be seen with the ordinary light microscope but can often be seen with the electron microscope, that are usually regarded as nonliving complex molecules, that have an outside coat of protein around a core of RNA or DNA, that can grow and multiply only in living cells, and that cause important diseases in plants and animals including human beings compare filterable virus
: a disease or illness caused by a virus
: a computer program that is usually hidden within another seemingly harmless program and that produces copies of itself and inserts them into other programs and usually performs a malicious action (as destroying data) comparetrojan horsesense 2, wormsense 5
: any of a large group of submicroscopic, infectious agents that are usually regarded as nonliving, extremely complex molecules or sometimes as very simple microorganisms, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, and plants