Virology is the scientific study of viruses and of the illnesses they cause. It is a branch of biology — sitting close to microbiology, but narrower, because viruses are a strange category of their own: far smaller than bacteria, unable to reproduce by themselves, and only able to make copies by getting inside a living cell and using that cell's machinery. So virology covers a lot: what a virus is built from, how it enters a cell, how it copies itself, how it changes over generations, how it passes between people or animals, and how vaccines and antiviral medicines can interrupt any of those steps. Clinical virology is the hospital side of it — testing patients' samples to find out which virus is making them sick. The word is an uncountable noun: you study virology, you work in virology, and there is no plural. Like most -logy words it can also stand for the *department* or the *discipline* as an institution: "she's in virology on the third floor." Until recently this was a specialist word that lived in universities. The pandemic years pushed it into ordinary news writing, so the word is now much more widely recognised than it was — though most people who say it would still struggle to say exactly where virology stops and immunology begins.

病毒學