(1) Any function which is the sum of constants times other constants to the power of the argument: f(x)=Σ_i=0^k c_ib_i^xp_i. (2) In complexity theory, the measure of computation, m(n) (usually execution time or memory space), is bounded by an exponential function of the problem size, n. More formally if there exists k > 1 such that m(n) = Θ(kⁿ) and there exists c such that m(n) = O(cⁿ).