1706, from Latin exponentem (nominative exponens), present participle of exponere "put forth" (see expound). A mathematical term at first; the sense of "one who expounds" is 1812. As an adjective, from 1580s.
A number or symbol, placed above and to the right of the expression to which it applies, that indicates the number of times the expression is used as a factor. For example, the exponent 3 in 53 indicates 5 × 5 × 5; the exponent x in (a + b)x indicates (a + b) multiplied by itself x times.
A number placed above and to the right of another number to show that it has been raised to a power. For example, 32 indicates that 3 has been raised to a power of 2, or multiplied by itself; 32 is equal to 9.