virus

noun

vi·​rus ˈvī-rəs How to pronounce virus (audio)
plural viruses
1
a
: 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
b
: a disease or illness caused by a virus
c
: the causative agent of an infectious disease
2
: something that poisons the mind or soul
the force of this virus of prejudiceV. S. Waters
3
: 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)
4
archaic : venom sense 1

Examples of virus in a Sentence

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 Web Two doses are 97% effective at preventing measles if a person is exposed to the virus. Katia Hetter, CNN, 14 Mar. 2024 Another had been in Idaho, which state health authorities linked to an unvaccinated adult who traveled to Europe, where many countries are now facing resurgent outbreaks of the virus. Alexander Tin, CBS News, 13 Mar. 2024 Unhoused people in encampments and congregate shelters broadly were at higher risk of exposure to the virus. Andrea Castillo, Los Angeles Times, 12 Mar. 2024 But there would not have been a Salk vaccine without the work of Isabel Morgan, a researcher at Johns Hopkins University who discovered three subtypes of the virus and helped develop an experimental vaccine that protected monkeys against polio. Alicia Ault, Smithsonian Magazine, 12 Mar. 2024 Common symptoms typically appear between 2-21 days after exposure to the herpes virus, but some might not start until months or years later.4 However, in rare cases, herpes can cause complications. Jennifer Sabour, Health, 9 Mar. 2024 Chewing gum is fighting more than a virus, however, when its comes to regaining its flavor. By dee-Ann Durbin, Quartz, 7 Mar. 2024 With nearly everyone in the U.S. having some degree of immunity against the virus (CDC estimates 98% of Americans have been infected or vaccinated or both), the consequences of infection in 2024 are just very different for the majority. Ashish K. Jha, STAT, 6 Mar. 2024 Anyone who was in the department's waiting and triage areas between 10:30 a.m. and 1:30 p.m. Friday may have been exposed, as the virus can live for up to two hours in the air. Jenna Prestininzi, Detroit Free Press, 3 Mar. 2024

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.

Word History

Etymology

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 "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

Note: 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.

First Known Use

1599, in the meaning defined at sense 4

Time Traveler
The first known use of virus was in 1599

Dictionary Entries Near virus

Cite this Entry

“Virus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/virus. Accessed 29 Mar. 2024.

Kids Definition

virus

noun
vi·​rus ˈvī-rəs How to pronounce virus (audio)
plural viruses
1
: 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
2
: a disease or illness caused by a virus
3
: 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) compare trojan horse sense 2, worm sense 5
Etymology

from Latin virus "poison, venom, secretion"

Medical Definition

virus

noun
vi·​rus ˈvī-rəs How to pronounce virus (audio)
1
a
: the causative agent of an infectious disease
b
: 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
c
: a disease caused by a virus
2
: an antigenic but not infectious material (as vaccine lymph) obtainable from a case of an infectious disease
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