Involution : function which is its own inverse

 

          (e.g.  If  f(x) = x / (x-1), then  f -1(x) = x / (x-1) = f(x).)

 

 

Contronym :  word which is its own opposite

 

            (e.g.  fast, which means moving quickly, as in “He ran fast.”, as well as not

            moving at all, as in “He held fast.”)

 

 

 

 

http://en.wikipedia.org/wiki/Involution

 

http://mathworld.wolfram.com/Involution.html

 

 

 

 


http://en.wikipedia.org/wiki/Auto-antonym

 

http://www.rinkworks.com/words/contronyms.shtml

   (nice list !!)