Smelly means having a strong bad smell. Here is the thing students miss: on its own, smelly is always negative. A flower is not smelly, however strong its scent — you would say fragrant, or sweet-smelling. Smelly is for socks, bins, drains, cheese, wet dogs, feet, an unwashed shirt. It is an everyday word, plain and slightly childish in flavour, used freely in speech and by children. It goes both before a noun (a smelly old jumper) and after be (this room is smelly), and it takes the usual endings: smellier, smelliest. It can also be aimed at a person as a mild insult — 'you're smelly' — which from a child is rude but not shocking. There is one gentle exception: some strong-smelling foods, especially cheese, get called smelly with real affection by people who love them. And the word does turn friendly when something is put in front of it — sweet-smelling flowers, nice-smelling soap — but that is the -smelling compound, not smelly by itself.