Virus
Etymology
From Latin "virus," meaning poison, venom, or slimy liquid. For centuries it just meant a noxious substance; only in the late 1800s, when researchers found infectious agents small enough to pass through filters that stopped bacteria, did it name this specific class of particle.
noun · /VY-rus/
A tiny infectious particle that can only reproduce by hijacking the cells of a living host.
What it names
Reach for it when you mean a pathogen too primitive to live on its own — genetic code in a shell that borrows a cell to copy itself.
Example
Because a virus isn’t truly alive on its own, antibiotics can’t touch it.
Related idea
A virus is not a living cell and must invade one to replicate, while bacteria are complete living cells that can grow and divide on their own. That difference is why bacterial infections often yield to antibiotics but viral ones usually don’t.
noun · /VY-rus/
A malicious program that copies itself into other files or computers.
What it names
self-replicating malicious software
Example
The virus spread through email attachments and wiped the drives.
Related idea
Named by analogy to the biological kind — it infects hosts and spreads by replication. Compare meme, another self-spreading unit.