A virologist is a scientist whose subject is viruses — what they are made of, how they get inside cells, how they change, how they spread, and how we might stop them. The word names the *person*, not the field; the field is virology. That distinction matters here, because the definition line you were given describes the field. If you are talking about the study itself, the word is virology. If you are talking about the human being in the lab coat, it is virologist. The -ist ending is doing the work: it turns a subject into a person who does it, exactly as in biologist, chemist, pianist, and dentist. A virologist may work in a university, in a hospital laboratory, at a public health agency, or in a company developing vaccines and antiviral drugs. Note that a virologist is not the same as an epidemiologist, though the news often mixes them: an epidemiologist studies how disease moves through a *population* — who catches it, how fast, and why — while a virologist studies the *virus itself*. During the COVID-19 years both kinds of scientist appeared on television nightly, which is how this once-technical word became something ordinary people say. It is a neutral, straightforward word. There is no informal version — you would simply say "a scientist who studies viruses" if you wanted to avoid it.

病毒學家