I just LOVE words!
I was recently trying to use the word cleave appropriately in my book, but I was struggling. So I looked up the definition and was struck by the fact that–depending on how you use the word–it can be its own opposite.
verb (used without object)
1. to adhere closely; stick; cling (usually followed by to).
verb (used with object)
1. to split or divide by or as if by a cutting blow, especially along a natural line of division, as the grain of wood.
Confused by my findings, I decided to look up the etymology of the word and found this hilarious observation: Biblically enjoined to “cleave unto his wife,” poor Henry VIII appears indeed to have got sadly confused between these two senses, though curiously not in the case of wife #4.
Apparently, “cleave” is something called a “contronym”, which are words that are their own opposites.
Thank you Ophelia Bell for pointing me in the direction of this list of contronyms, many of which we use in everyday language. http://mentalfloss.com/article/49834/14-words-are-their-own-opposites