Though the tidy line you may see calls this an oil, naphthalene is not really an oil you pour. It is a white solid, often in little balls or flakes, with a very strong smell. The famous home use is mothballs: the balls people put with winter clothes to keep small insects away. Chemists get it from coal tar or from oil, and they use it to make dyes, plastics, and other chemicals. The cousin word naphtha is the oil-like fuel used for making chemicals — the two names look alike, and that is why the “oil” story gets stuck to the wrong word. If it smells like mothballs, you are looking at naphthalene.

萘（店裡的「樟腦丸／衛生球」有時其實是萘，不是真正的樟腦）