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
Ashlyn Needham, Southern Living, 28 Dec. 2025
Avoid using abrasive or flammable cleaners on stainless steel surfaces to prevent damage and safety hazards.
—Alicia Chilton, Better Homes & Gardens, 23 Dec. 2025
Hazardous and flammable items such as batteries, gas containers and chemicals, should not be placed in garbage and recycling carts, the city says.
—Evan Moore, Charlotte Observer, 22 Dec. 2025
While plants and landscaping are the chief focus, the law also applies to fencing, patios and decks made of wood or other flammable materials.
—David Garrick, San Diego Union-Tribune, 21 Dec. 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 1 Jan. 2026.
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flammable
adjective
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