flammable
adjective
Usage of Flammable, Inflammable, and Nonflammable
Flammable and inflammable look like opposites, but they both describe something that ignites easily and burns quickly. Inflammable arrived in English two centuries before flammable. Its prefix in- is not the one meaning "not," familiar from words like inactive and inaccurate. Instead it is another prefix altogether: in- as a form of -en-, meaning "to cause to be," as in the words indent and indebted. This fact is not obvious, however, and confusion about the meaning of inflammable persists. Using nonflammable is one way to ensure clarity when "not flammable" is the intended meaning.
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Why Inflammable Is Not the Opposite of Flammable
Combustible and incombustible are opposites but flammable and inflammable are synonyms. Why? The in- of incombustible is a common prefix meaning "not," but the in- of inflammable is a different prefix. Inflammable comes from Latin inflammare ("to inflame"), itself from in- (here meaning "in" or "into") plus flammare ("to flame"). Flammable also comes from flammare. In the early 20th century, firefighters worried that people might think inflammable meant "not able to catch fire," so they adopted flammable and nonflammable as official safety labels and encouraged their use to prevent confusion. In general use, flammable is now the preferred term for describing things that can catch fire, but inflammable is still occasionally used with that meaning as well.
Examples of flammable in a Sentence
Lisa Gutierrez, Kansas City Star, 24 Nov. 2025
The museum digs into its expansive collection of rare (and highly flammable) nitrate films and hosts a series of screenings all tinged with the thrill of risk.
—The Atlantic, 19 Nov. 2025
Residents and visitors are urged to properly dispose of cigarette butts, matches, and any other flammable items in appropriate containers.
—Nc Weather Bot, Charlotte Observer, 18 Nov. 2025
That’s because well-off Angelenos tend to live on mountains and hillsides and in canyons that are covered in highly flammable chaparral, which are an excellent breeding ground for rapidly spreading fires, driven by Santa Ana winds of up to 100 mph.
—Todd Longwell, Variety, 12 Nov. 2025
See All Example Sentences for flammable
Cite this Entry
“Flammable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/flammable. Accessed 30 Nov. 2025.
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flammable
adjective
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