Use flammable to describe something that can catch fire and burn easily, particularly when talking about materials and substances. Because of its clear and direct meaning, flammable is the preferred term in safety communications, product labels, and guidelines to convey the risk of fire without ambiguity.

Inflammable also indicates that a material can easily catch fire, however, its use is discouraged in safety contexts to prevent confusion with its false antonym, non-inflammable. If you come across the term inflammable, recognize that it has the same meaning as flammable and implies a fire hazard.

Although they appear to have differing prefixes, flammable and inflammable both describe materials that catch fire easily. The term inflammable might be misleading due to its prefix, while flammable is straightforward and clear, making it the preferred term for safety messages. Both words are adjectives and pronounced with a similar stress pattern, yet today, flammable is more widely accepted to mitigate confusion and promote clarity in communication about fire hazards.