virus
Word family
Synonym discussion
Sense: noun/1
Germ is the broadest everyday term for any tiny organism that makes you sick — it includes both viruses and bacteria. Pathogen is a formal scientific label for any disease-causing agent, whether a virus, bacterium, or fungus; you are more likely to see it in medical textbooks than in conversation. Microbe is even wider and refers to any microscopic living thing, many of which are harmless or even helpful; calling a virus a microbe is technically correct but loses the sense of threat. Bug is the informal, friendly word for a minor illness: you might say 'I picked up a bug' after a party, but it sounds odd for serious diseases. In short, use virus when you want to be specific about the cause, germ for everyday illness talk, and pathogen for formal or scientific writing.
Common collocations
Etymology
The word virus comes directly from Latin, where it meant 'poison', 'slime', or 'venom'. In the 1700s, English medical writers began using it for any substance that could transmit disease. By the late 1800s, scientists had identified actual microscopic agents and kept the same word. The computer-virus sense appeared in the 1970s and became widely known in the 1980s, drawing a deliberate parallel between biological infection and the way malicious code copies itself through computer systems. The figurative sense grew naturally out of the same analogy.