?

[McNoodle]

How come flammable and inflammable mean the same?

[stewey]

McNoodle, In North America, the term "inflammable" indicates that the material it refers to is not flammable.

[dr john]

Their roots are different though related: flammable means capable of flaming, inflammable capable of becoming inflamed (so the in- part is not a negative).

[Quizmonster]

In the 1950s, the British Standards Institution revived the word �flammable', hoping that it would be adopted in place of �inflammable' which means exactly the same thing. The latter comes from the Latin word �inflammare', meaning to burst into flame. The key point is that the �in' part of that word never was a negative form in the way in which �invisible' is the opposite of �visible'. The Institution wished �non-flammable' to be the opposite.
The problem is that - although manufacturers and official bodies adopted these new ideas - ordinary people didn't. They remained convinced that putting �in' in front of a word rendered it into its opposite...end of story! (In)compatible, (in)sufficient, (in)voluntary and a host of other words were good enough reason for the British public to stick to its guns. In this case, they are simply �wrong'.

[McNoodle]

We just haven't grasped it over here stewey.