Provex

Provex: adjective. The opposite of “convex”. This word was invented in 1973 when a student was trying to complete his homework but forgot the word “concave”, unable to remember it he decided to use the word “provex” (incidents where people use the word “provex” because they can’t think of “concave”  have been done by people who didn’t even know of this word’s previous existence so it can be assumed that the event took place before then, but as that student presented the first recorded case of it happening (this may have happened before but it’s difficult to tell because the word may have just been a part of their language), but this was the first recorded case and therefore is the case that is credited for the word). Other than just replacing a word on cannot remember; this word is also used to add variety in the vocabulary of one’s writing, especially if they happen to be writing a story about concave caves with walls that bend inward and there are many indented features on depressions in the ground.