Exponent
Part of speech: noun
Definition: One who expounds, represents or advocates The power to which a number, symbol or expression is to be raised. As in the 3\, in x^3\,.
Advocate
Part of speech: verb
Definition: To argue for someone else.To encourage support for something.
Part of speech: noun
Definition: A person who argues the case of another, such as a lawyer in a court.A person who speaks in support of something.A person who supports someone to make their voice heard, or ideally to speak up for themselves.
Example sentence: To advocate a New Order was to seek freedom and respect for peoples without prejudice, and to seek a stable basis for the existence all peoples, equally, and free of threats.