Exponent (noun)

1. A symbol indicating the power to which a quantity is to be raised, as in a^n.
2. A person who advocates or exemplifies a particular cause or theory.

Origin:

From latin exponentem, present participle of exponere "to set forth, explain, show".

Examples:

1. The exponent of the term a^3 is 3.
2. Einstein is considered an exponent of the theory of relativity.
3. She's a well-known exponent of feminist literature.
4. The exponent of the number 2^4 is 4.
5. He is an exponent of the new school of thought.