Definition of exponent noun from the Oxford Advanced Learner's Dictionary

exponent

noun
ɪkˈspəʊnənt
 
; ɪkˈspoʊnənt
 
 
1 a person who supports an idea, theory, etc. and persuades others that it is good
Synonym
proponent
She was a leading exponent of free trade during her political careerHuxley was an exponent of Darwin's theory of evolution.
2 a person who is able to perform a particular activity with skillthe most famous exponent of the art of mime3 (mathematics) a raised figure or symbol that shows how many times a quantity must be multiplied by itself, for example the figure 4 in a4