>>>>How about the use of the prefix "in". Why is "invisible" the opposite of "visible" but "inflammable" is not the opposite of "flammable".
>>>
>>>Because, IIRC, "flammable" is a late addition. The right word is "inflammable," meaning that it can go into flames.
>>>
>>>Tamar
>>
>>Ok that maybe so, but evenmore, if "inflammable" was the original word, the "in" prefix should make it the complete opposite of "can go into flames". Take these other word pairs for example, visible/invisible, competent/incompetent, active/inactive, complete/incomplete. As you know, there are many more.
>>
>>Mike
>
>Yeah, and nocent/innocent (so "nocent" is another word for "guilty"?), novative/innovative ("novative" means "incapable of coming up with new ideas")
>
>IOW not all words beginning with "in" are necessarily the opposite of another. The opposite of (in)flamable is non-flammable.

Yes, and it all boils down to "there are rules and they are meant to be broken" in the English language. You know, like "'i' before 'e' except after 'c'" ;P