View synonyms for virus


[ vahy-ruhs ]


, plural vi·rus·es.
  1. an ultramicroscopic (20 to 300 nanometers in diameter), metabolically inert, infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals: composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding envelope.
  2. a viral disease:

    He stayed home sick with a virus for nearly two weeks.

  3. a corrupting influence on morals or the intellect; poison.
  4. a segment of self-replicating code planted illegally in a computer program, often to damage or shut down a system or network.


/ ˈvaɪrəs /


  1. any of a group of submicroscopic entities consisting of a single nucleic acid chain surrounded by a protein coat and capable of replication only within the cells of living organisms: many are pathogenic
  2. informal.
    a disease caused by a virus
  3. any corrupting or infecting influence
  4. computing an unauthorized program that inserts itself into a computer system and then propagates itself to other computers via networks or disks; when activated it interferes with the operation of the computer
“Collins English Dictionary — Complete & Unabridged” 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012


/ rəs /

, Plural viruses

  1. Any of various extremely small, often disease-causing agents consisting of a particle (the virion ), containing a segment of RNA or DNA within a protein coat known as a capsid . Viruses are not technically considered living organisms because they are devoid of biological processes (such as metabolism and respiration) and cannot reproduce on their own but require a living cell (of a plant, animal, or bacterium) to make more viruses. Viruses reproduce first either by injecting their genetic material into the host cell or by fully entering the cell and shedding their protein coat. The genetic material may then be incorporated into the cell's own genome or remain in the cytoplasm. Eventually the viral genes instruct the cell to produce new viruses, which often cause the cell to die upon their exit. Rather than being primordial forms of life, viruses probably evolved from rogue pieces of cellular nucleic acids. The common cold, influenza, chickenpox, smallpox, measles, mumps, yellow fever, hemorrhagic fevers, and some cancers are among the diseases caused by viruses.
  2. Computer Science.
    A computer program that duplicates itself in a manner that is harmful to normal computer use. Most viruses work by attaching themselves to another program. The amount of damage varies; viruses may erase all data or do nothing but reproduce themselves.


  1. plur. viruses Microorganisms consisting of DNA and RNA molecules wrapped in a protective coating of proteins . Viruses are the most primitive form of life. They depend on other living cells for their reproduction and growth. ( See under “Medicine and Health.” )


  1. plur. viruses A minute organism that consists of a core of nucleic acid surrounded by protein . Viruses, which are so small that a special kind of microscope is needed to view them, can grow and reproduce only inside living cells . ( See under “Life Sciences.” )


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Viruses cause many diseases. ( See viral infection .)
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Derived Forms

  • ˈvirus-ˌlike, adjective
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Other Words From

  • vi·rus·like adjective
  • an·ti·vi·rus adjective
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Word History and Origins

Origin of virus1

First recorded in 1590–1600; from Latin vīrus “slime, poison”; akin to Sanskrit viṣá-, Avestan viša-, Greek iós (from earlier wiós, from still earlier wisós ), all meaning “poison, venom”
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Word History and Origins

Origin of virus1

C16: from Latin: slime, poisonous liquid; related to Old English wāse marsh, Greek ios poison
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Example Sentences

By September 10, there was a 44 percent increase in the proportion of people over age 75 who have been diagnosed with the virus compared to the previous week.

From Vox

These viruses circulate year-round in the tropics but are more common during the rainy season.

That is when Eckard Wimmer, a virologist at Stony Brook University, caused a sensation by creating infectious polio virus starting from only genetic instructions.

“Once a cell is infected, it is completely taken over by the virus, producing an astonishing number of viruses,” Ehre says.

By April, waves of workers who debone chickens or carve up pork elbow-to-elbow with their co-workers were falling ill from the virus.

The vaccine is delivered through a “carrier virus” that causes a common cold in chimpanzees but does not affect humans.

He became delirious, his heartbeat grew ragged, his blood teemed with the virus, and his lungs, liver and kidneys began to fail.

By May 27, five people had succumbed to the virus and 16 more were infected.

The current FDA-approved measles vaccine consists of live but weakened measles virus that is injected into the arm.

The fact that the virus is still alive has sustained many safety concerns, both rational and irrational, about its use.

If there is neuritis from the virus it becomes intense and causes muscular contractions, paresis, and paralysis.

(p. 442) But it was the more poisonous virus of Secession which finally laid their proud city low.

The scientists of Sator knew that the virus was virulent; in fact, too virulent for its own good.

They knew that shortly after every Nansalian died, the virus, too, would be dead.

It killed the host every time, and the virus could not live outside a living cell.


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What Is The Plural Of Virus?

Plural word for virus

The plural form of virus is viruses (not viri). Even though virus is derived from Latin, it isn’t pluralized by replacing the -us ending with -i, as is done in many other Latin-derived words ending in -us, such as cactus/cacti and fungus/fungi.

Most words ending in -s, -ss, -ch, -sh, -x, and –o follow the conventional pluralization pattern of simply adding -es. However, several other words that end in -us are pluralized in the same way as virus, such as surplus/surpluses and census/censuses.

More About Virus

What is a virus?

A virus is an ultramicroscopic agent that can only reproduce in living cells and is spread through infection. Many viruses cause diseases as part of their reproduction process.

Viruses are only 20 to 300 nanometers—so small that even microscopes can’t see them. Viruses are also very simple. They consist of a core made of DNA or RNA, a protein coat that surrounds the core, and sometimes an envelope that surrounds the core.

A virus can’t reproduce on its own. Instead, it will infect a living cell and force it to make more copies of the virus. When the virus does this, it stops the cell from whatever it was doing before and, eventually, kills the cell.

Viruses are infectious, meaning they often cause symptoms that allow fluids with copies of the virus to spread to other organisms. For example, if you have the flu and cough on another person, your virus-containing saliva and mucus will enter the other person’s body and allow the virus to infect their cells.

Because viruses remain inside living cells, it is often impossible to kill the virus without also killing the cell. Usually, your immune system is the only thing that can safely fight a virus.

Why is virus important?

Viruses are responsible for some of the most deadly, incurable diseases we have today. In 2019, a new type of coronavirus (a family of viruses that often cause respiratory illnesses) was the cause of a deadly disease known COVID-19 (short for coronavirus disease 2019), which became a worldwide pandemic.

Viruses have also been responsible for other serious diseases, such as HIV (short for human immunodeficiency virus), that causes AIDS, a disease in which the immune system gradually breaks down and often leads to cancer.

Because viruses are so hard to kill and some can make you very sick, we try to prevent viruses from infecting us in the first place. Washing your hands, not breathing on people, and staying home when you are sick with a virus all help prevent the virus from spreading.

Vaccines are used to train your immune system to better fight specific viruses. Sometimes, antiviral medications can interfere with the virus’s ability to take over a cell or treat the symptoms of the virus rather than attack the virus itself.

Did you know ... ?

The word virus is also used to describe malicious computer code that is designed to harm or infect computers in a similar way to how a biological virus infects living things.

What are real-life examples of virus?

What other words are related to virus?

Quiz yourself!

True or False?

Because viruses are hard to kill, we try to prevent them from spreading in the first place.




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