n.  1.  (Alg.) A number, letter, or any quantity written on the right hand of and above another quantity, and denoting how many times the latter is repeated as a factor to produce the power indicated  
2.  One who, or that which, stands as an index or representative;  
3.  one who explains, expounds, or interprets.

Noun  1.  exponent  a person who pleads for a cause or propounds an idea 
2.  exponent  someone who expounds and interprets or explains  
3.  exponent  a mathematical notation indicating the number of times a quantity is multiplied by itself 
(programming)  exponent  (Or "characteristic") The part of a floatingpoint number specifying the power of ten by which the mantissa should be multiplied. In the common notation, e.g. 3.1E8, the exponent is 8. 