subexponential

Slower than every exponential sequence: $|a_k|=e^{-g(k)}$ for some $g(k)$ that grows sublinearly.

Includes polynomials, logarithms, and their products, e.g. $\frac{1}{k}$, $\frac{1}{k^2}$, $\frac{1}{\log k}$, etc.