She's On Fire!

If something is flammable, according to Dictionary.com, it is "easily set on fire; combustible; inflammable."

That's right. Inflammable and flammable mean the same thing: easily ignited. So which came first, the chicken or the egg? Well, it seems that the word inflammable actually predates its more abbreviated version by about 200 years and, in fact, flammable only came about because inflammable was commonly mistaken to mean "nonflammable." Just imagine the consequences. In this case, the difference is huge.

According to The Columbia Guide to Standard American English:

Flammable and inflammable are synonyms, both meaning 'susceptible of or capable of catching fire and burning rapidly.' Inflammable was the word of choice for a long time, but fire-fighting associations and insurers, apparently concerned that the in- prefix would be misunderstood to mean 'un-' or 'non-' (which in another in prefix it does) decided to remove all doubt by labeling materials, gasoline trucks, and other things that can burn flammable. Both words are still in use, and both are Standard. Nonflammable, incombustible, and noncombustible are antonyms of flammable and inflammable: they mean 'fireproof.'

Dictionary.com explains it this way:

Inflammable and flammable both mean 'combustible.' Inflammable is the older by about 200 years. Flammable now has certain technical uses, particularly as a warning on vehicles carrying combustible materials, because of a belief that some might interpret the intensive prefix in- of inflammable as a negative prefix and thus think the word means 'noncombustible.' Inflammable is the word more usually used in nontechnical and figurative contexts: The speaker ignited the inflammable emotions of the crowd.

Wait a minute, so inflammable=flammable, but incombustible is the opposite of combustible? Yep. It's one of the (many) confusing beauties of our language. And to make matters even more confusing, although genius and ingenious mean virtually the same thing -- though be sure note the difference in spelling, not only concerning the existence or absence of the prefix 'in' -- the same is not true for famous and infamous. Unlike famous, infamous has a negative connotation.

Nonplussed yet? Relax. Just don't go lighting a match near anything that is "flammable" or "inflammable." In fact, a good rule of thumb might just be to avoid lighting matches near unknown substances no matter what. After all, as our good friend Smoky says, "Only you can prevent forest fires."