Inflammable or Flammable?

Who hasn’t quoted The Simpsons, when Doctor Nick rightfully exclaims “Inflammable means flammable? What a country!” Do you even know why flammable and inflammable mean the same thing? He asks the question and it's hilarious, but it really does make sense that he would, especially considering English does not appear to be his first language. Generally, words that begin with the prefix “in-” mean the opposite of the word it’s attached to. Capable and incapable, consistent and inconsistent, subordinate and insubordinate, are just a few examples of the many that exist. There’s even combustible and incombustible, combustible meaning it can catch fire and incombustible meaning it can’t. So, why do the words flammable and inflammable mean the exact same thing? This definitely seems like an easy way for people to get hurt or killed.

The definition of the word flammable is “easily set on fire; combustible; inflammable.” The definition of the word inflammable is “capable of being set on fire; combustible; flammable.” They both originate from Latin, flammable first being used sometime between 1805 and 1815, while inflammable was part of vernacular earlier, starting usage sometime between 1595 and 1605. Inflammable comes from the Latin word inflamma, to inflame. Flammable comes from the Latin word flamma, to set on fire. So why are both of these words used when they seem like they would have the opposite definition, but in fact mean the exact same thing?

The prefix “in-” does not always serve as being negative. Sometimes it’s an intensifier, such as the word intense. Sometimes it means “into, on, in, upon” such as the words income, intake, and implant. This definition would cause inflammable to mean flammable from within. The actual antonyms of the words are non-flammable, non-inflammable, incombustible, non-combustible, and ininflammable. That’s right: ininflammable. English can be so confusing at times.


A bunch of flammable gas tanks

In around the 1920s, the National Fire Protection Association (NFPA) started to urge Americans to use only the word flammable due to the possibility of people being confused. Even during World War II, American companies were urged to use only “flammable” when labelling explosives being sent to Europe, in order to avoid fatal accidents. Inflammable started to fall out of favor in around 1970, and now it’s somewhat rare to see the word being used over flammable.

English can be a very strange language at times, but now, hopefully, you understand it a little bit more. Surely now, you’ll be a bit more cautious when you see a sign or label that says inflammable.


Barak Bacharach, SkySaver Content Manager