A non-smoker is a person who does not smoke — in ordinary talk, that means they do not smoke cigarettes, cigars, or a pipe. People use it when health, jobs, hotels, and dating come up: “I’m a non-smoker” is a short way to tell others you do not use tobacco that way. Though actually, the edges are messy. Someone who used to smoke but has stopped is usually called a non-smoker now, and so is someone who never smoked at all; the word does not tell you which. It also usually points at tobacco smoke, not every kind of smoke. A person who does not smoke cigarettes but uses something else may still call themselves a non-smoker, and other people may not agree. In writing it almost always keeps the hyphen.