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
Ashley MacKin Solomon, San Diego Union-Tribune, 26 Oct. 2025
In the late twentieth century, fire agencies urged homeowners to replace flammable wooden shingles with alternatives such as Spanish tiles, which are made from non-combustible terra-cotta.
—Ingfei Chen, New Yorker, 22 Oct. 2025
Assembly Bill 888 establishes a grant program aimed at helping low- and middle-income homeowners in high-fire-risk areas to pay for the removal of flammable vegetation and implement other mitigating measures—like installing fire-resistant materials—within 5 feet of their homes.
—Giulia Carbonaro, MSNBC Newsweek, 21 Oct. 2025
For maximum effectiveness, gas detectors should be installed low to the ground near gas appliances, since most flammable gases are heavier than air.
—Lauren Bengtson, Better Homes & Gardens, 21 Oct. 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 9 Nov. 2025.
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flammable
adjective
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