Inflammable & Flammable

Inflammable (pronounced in-flam-uh-buhl)

(1) Easily set on fire; combustible; incendiary, combustible, inflammable, burnable, ignitable (recommended only for figurative use).

(2) Easily aroused or excited, as to passion or anger; irascible; fiery; volatile, choleric.

1595–1605: From the Medieval Latin inflammābilis, the construct being the Classical Latin inflammā(re) (to set on fire) + -bilis (from the Proto-Italic -ðlis, from the primitive Indo-European i-stem form -dhli- of -dhlom (instrumental suffix).  Akin to –bulum, the suffix -bilis is added to a verb to form an adjectival noun of relationship to that verb (indicating a capacity or worth of being acted upon).  Construct of the Classical Latin inflammare (to set on fire) is -in (in, on) + flamma (flame).

Flammable (pronounced flam-uh-buhl)

Easily set on fire; combustible; incendiary, combustible, inflammable, burnable, ignitable

1805–1815: From the Classical Latin flammā(re) (to set on fire) + -ble (the Latin suffix forming adjectives and means “capable or worthy of”).

Need for standardization

Flammable and inflammable mean the same thing.  English, a mongrel vacuum-cleaner of a language, has many anomalies born of the haphazard adoption of words from other tongues but the interchangeability of flammable and inflammable is unfortunate because of the use in signs to warn people of potentially fatal danger.

In- is often used as a prefix with adjectives and nouns to indicate the opposite of the word it precedes (eg inaction, indecisive, inexpensive etc).  Given that, it’s reasonable to assume inflammable is the opposite of flammable and that objects and substances should be so-labeled.  The reason for the potentially deadly duplication is historic.  Inflammable actually pre-dates flammable, the word derived from the Latin verb inflammare (to set on fire), this verb also the origin of the modern meaning “to swell or to provoke angry feelings”, hence the link between setting something on fire and rousing strong feelings in someone.  So, at a time when Latin was more influential, inflammable made sense.  However, as the pull of Latin receded, words with in- (as a negative prefix) became a bigger part of the lexicon and the confusion was created.  By the early nineteenth century, flammable had become common usage, and by the twentieth was widespread.  The modern convention is to use flammable literally (to refer to things which catch fire) and inflammable figuratively (to describe the arousal of passions, the swelling of tissue etc.  Surprisingly, the rules applying to warning signs have yet to adopt this standardization.

Using flammable and inflammable to mean the same thing is confusing.  The preferred wording is flammable and non-flammable.  Borrowing from semiotics, danger should be indicated with red, safety with green.