Word Confusion: Flammable versus Inflammable

Posted July 4, 2016 by Kathy Davie in Author Resources, Editing, Self-Editing, Word Confusions, Writing

This seemed so appropriate for a Fourth of July post. And even more cause for celebration is that *insert fireworks here* the two words are interchangeable.

The confusion arises with that bloody prefix. We tend to interpret in- as not, opposite of, or without. So it made sense to believe inflammable is the opposite of flammable.

Instead, inflammable uses a different in- prefix meaning into; it intensifies the meaning of the base word.

Oh, yeah, I knew that…*eye roll*…

Musing on Which to Choose

Use flammable in technical situations; there is less risk of confusion amongst your readers. Using inflammable is likely to create the opposite impression of what you intended. Even manufacturers don’t use the term inflammable as the people who use flammable products think inflammable means the opposite.

Inflammable is more commonly used in emotional or metaphorical contexts.

Whichever one you choose, be consistent in using that version!!

Word Confusions…

…started as my way of dealing with a professional frustration with properly spelled words that were out of context in manuscripts I was editing as well as books I was reviewing. It evolved into a sharing of information with y’all. I’m hoping you’ll share with us words that have been a bête noir for you from either end. Consider sharing this Word Confusion with friends by tweeting it.

Flammable Inflammable
Credit to: Apple Dictionary.com; Dictionary.com: inflammable; Cambridge Dictionary: inflammable

A propane tank

Image is Editor abcdef’s own work [CC0], via Wikimedia Commons

A flammable gas tank.

A watercolor by Thomas Rowlandson depicting an inflamed mob protesting outside a doctor's house.

Image by Thomas Rowlandson [CC BY 4.0], via Wikimedia Commons

This inflammable mob is quite roused up.

Part of Grammar:
Adjective Adjective
Noun plural: inflammables
Easily set on fire

Liable to catch fire

  • Readily combustible
  • Inflammable
Easily set on fire

Easily aroused or excited, as to passion or anger

  • Likely to become violent or angry very quickly and in an uncontrolled way
  • Irascible
  • Excitable

Something that is liable to catch fire

As the first little pig found out, a wooden house uses highly flammable materials.

Manufacturers use the adjective flammable on products carrying or made of combustible materials.

A few decades ago, a law was passed requiring children’s pajamas be made from non-flammable fabrics.

The speaker ignited the inflammable emotions of the crowd.

The building had filled with inflammable and poisonous gases.

Jenny had to be so careful in what she said, as Jake had an inflammable temper.

“See if you can find anything inflammable around: fuel for that, for instance.” – John Pritchard, Night Sisters

The truck is packed with inflammables.

Noun: flame, flammability
Verb: flame
Adjective: noninflammable, uninflammable
Adverb: inflammably, noninflammably
Noun: inflamer, inflammability, inflammableness, inflammation, noninflammability, noninflammableness
Verb: inflame
History of the Word:
Early 19th century from the Latin flammare, which is from flamma meaning a flame. Early 17th century from the Old French enflammer or the Latin inflammare, which is from in- (into) + flamma (flame).

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C’mon, get it out of your system, bitch, whine, moan…which words are your pet peeves?

Photo of Kathy Davie

Kathy Davie is an editor, author, and artist with degrees in Technical Writing & Editing, Digital Media, and History from Metropolitan State College in Denver, Colorado.

A huge believer in knowledge being power, Kathy has an ongoing and free set of Author Tools for authors interested in self-editing with an ongoing series of posts on Word Confusions, what’s Properly Punctuated, those tricky Formatting Tips, and the sleep-inducing Grammar Explanations. There is also an online tutorial on Using Microsoft Word’s Markup Tool.

And if you get too sleepy, explore KD Did It for various writing and editing services.

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