Inflammable means easily set on fire or capable of burning quickly. If something is inflammable, it can catch fire and burn rapidly, sometimes with little warning. Gasoline is highly inflammable: a single spark near spilled gasoline can cause it to burst into flames. Dry leaves, paper, and certain chemicals are also inflammable.

Here's where this word gets confusing: inflammable means exactly the same thing as flammable. You might think the “in” at the beginning means “not,” like in words such as invisible or incomplete. But in this case, inflammable still means something that can burst into flames.

Because this confusion could be dangerous, especially on warning labels, most safety signs today use flammable instead of inflammable. Both words mean the same thing, but flammable is clearer and harder to misunderstand. If you see “flammable” or “inflammable” on a container, the message is identical: keep it away from heat, sparks, and flames, because it can catch fire easily.