Difference between flammable and inflammable

This is part of the difference between series.

I’ve heard some people confusing the words flammable and inflammable. Here’s the difference between the two.

Actually, there’s no difference; inflammable and flammable are synonymous.

The assumption that they have opposite meanings may derive from the fact that inflammable has an in- prefix, which typically has a negative connotation:

  • invisible
  • incapable
  • inexpensive

However, the root of inflammable is inflame (sometimes spelled enflame). Inflame has multiple meanings today, a popular one being to provoke to anger. Another meaning, however, is to set on fire. Inflame comes from the Latin inflammare (flammare, “to catch fire”; in-, “to cause to”).

Other English words using the in- prefix that don’t have a negative meaning include:

  • inscribe
  • inquire
  • impress
  • immigrate

Inflammable has been around for 200 years longer than flammable, so arguably, it’s more correct. That being said, a lot of people think it’s incorrect, so if you use it, tread carefully.

Which words do you confuse? Let me know in the comments below.

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By Kim Siever

I am a copywriter and copyeditor. I blog on writing and social media tips mostly, but I sometimes throw in my thoughts about running a small business. Follow me on Twitter at @hotpepper.

2 comments

  1. So then what is the word one should use that refers to something that is not flammable (will not catch on fire)?

    1. You have a few options: fireproof, flameproof, incombustible, non-flammable. :)

      Sorry for the late response.

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