Historically, flammable, inflammable and combustible meant capable of burning. The word "inflammable" came through French from the Latin inflammāre = "to set fire to", where the Latin preposition "in-" means "in" as in "indoctrinate", rather than "not" as in "invisible" and "ineligible".
The word "inflammable" may be erroneously thought to mean "non-flammable". The erroneous usage of the word "inflammable" is a significant safety hazard. Therefore, since the 1950s, efforts to put forward the use of "flammable" in place of "inflammable" were accepted by linguists, and it is now the accepted standard in American English and British English.  Antonyms of "flammable" or "inflammable" include: non-flammable, non-inflammable, incombustible, non-combustible, not flammable, and fireproof.
Flammable applies to combustible materials that ignite easily and thus are more dangerous and more highly regulated. Less easily ignited less-vigorously burning materials are combustible. For example, in the United States flammable liquids, by definition, have a flash point below —where combustible liquids have a flash point above . Flammable solids are solids that are readily combustible, or may cause or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty substances that easily ignite by brief contact with an ignition source, such as a burning match, and spread flame rapidly. The technical definitions vary between countries so the United Nations created the Globally Harmonized System of Classification and Labeling of Chemicals, which defines the flash point temperature of flammable liquids as between 0 and  and combustible liquids between  and .