Grammar is important, but English grammar so often confuses us by going against it’s own rules time and time again. A classic example of the confusion that is inherent to the english language are the words flammable and inflammable.
If we use our 6th sense of grammar, we would assume that these two words mean opposite things. After all, sane and insane, active and inactive, edible and inedible are all opposites. Thus, it would make sense that flammable and inflammable would be like all those other pairs.
Reality check, they aren’t. Flammable and inflammable mean the exact same thing. How did this happen, you ask?
We can blame Latin for this one. The English prefix in- generally negates whatever comes after it because it is evolved from the Late prefix un- meaning “not”. However, the in- that begins inflammable comes from the Latin prefix en- meaning “to cause to be”. Instead of negating the word following, it intensifies it.
Due to this confusion, there were a lot more people accidentally setting things on fire than anyone was comfortable with, so in the 1920s the National Fire Protection Agency advocated to change all official warning signs to “flammable”.
Regardless of which is used, just remember not to light any matches around these words.