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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About Kim Siever

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

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