Flammable and inflammable

If something catches alight easily is it flammable or inflammable?

Both. Flammable and inflammable mean the same thing.

• Flammable means able to be set aflame, easily set on fire.
• Inflammable means able to be set aflame, easily excited or disturbed.

Confused?

We usually think of words that start with the prefix in being the opposite of the original word.

active and inactive
flexible and inflexible
organic and inorganic

However, the confusion can be blamed on a quirk of history. We get inflammable from the Latin inflammare, but in 1813 a scholar coined the English word flammable from the Latin flammare giving us two words with the same meaning.

To avoid this confusion, nonflammable is used to mean ‘not easily set alight’.

My recommendation is to use flammable and nonflammable and forget about inflammable, which is declining in usage.

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