Acetone is a clear liquid with a strong, sharp smell. People use it to clean surfaces, to make paint thinner so it spreads more easily, and in factories to make other chemicals. It dries very fast and it can catch fire, so you keep it away from flames. In everyday life, though, many people meet it as nail-polish remover — and that is often what they mean when they say acetone, even though chemists use it much more widely as a solvent (a liquid that dissolves other things). It belongs with the ketones; acetone is the simple one in that chemical family. Do not mix it up with acetylene, which is a gas for welding, even though the two names look alike.