Webster's English Dictionary

exponent

ex.po.nent \ik-'spo--n*nt, 'ek-.spo--\ n [L exponent-, exponens, prp. of 
   esponere] 1: a symbol written above and to the right of a mathematical 
   expression to  indicate the operation of raising to a power {in the 
   expression a3, the ~ 3 indicates that a is to be multiplied by itself 
   twice} 2a: one that expounds or interprets  2b: one that champions, 
   advocates, or exemplifies