What does virus mean?
A virus is an infectious agent that reproduces within a living host and can cause disease in humans, animals, and plants. Because viruses depend on host cells for replication, they differ fundamentally from bacteria, which are single-celled organisms capable of reproducing independently. The word also has a well-established computing meaning: a malicious program that spreads by copying itself into files, programs, or systems. More broadly, people describe unwanted influences as viral when they spread rapidly, such as a rumor, fashion, or harmful ideology. In these contexts, the word has strong negative associations with disease, damage, and contamination. It is also the source of related terms including viral, meaning spreading rapidly or caused by a virus; virulence, referring to the severity of disease-causing power; and virology, the study of viruses. Across biology, computing, and figurative language, virus is a useful word for describing something that spreads through a system and affects its host.
An infectious agent that reproduces within a living host and causes disease; also, a malicious computer program that spreads by copying itself, or a harmful influence that spreads rapidly.
"The virus infected several computers on the network."
The biological and computing senses are both standard. Figurative uses commonly describe rumors, behaviors, ideas, or influences that spread rapidly and are usually viewed negatively.
To infect a computer or file with a computer virus.
"The attachment was intended to virus the computer."
This verb is informal and much less common than the noun.
The standard plural is viruses, with the stress on the first syllable.
"Several viruses were detected in the laboratory samples."
The word virus comes from Latin for poison, a fitting origin for agents that can spread disease and disruption wherever they go.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does virus come from?
Virus comes from Latin, where virus originally meant poison, venom, or poisonous material. The word was applied to disease-causing agents before modern microscopy made viruses directly observable, and its scientific sense developed as microbiology advanced. Its broader computing and figurative uses came later by analogy with the way biological viruses spread and reproduce. The Latin root also underlies words such as virulent, virulence, virology, and virologist.
Related word forms
How virus is actually used
In biological contexts, virus is standard technical vocabulary and is not restricted to human disease. In computing, it is commonly used for self-replicating malicious software. Figurative uses are common and often carry negative connotations, especially in discussions of harmful ideas, behavior, or influence.
Easily confused with virus
A virus generally requires a living host cell to reproduce, whereas a bacterium is a single-celled organism that can often reproduce independently.