Definition:Little-O Notation/Sequence/Definition 2

Definition
Let $\left \langle {a_n} \right \rangle$ and $\left \langle {b_n} \right \rangle$ be sequences of real or complex numbers. Let $b_n\neq0$ for all $n$.

$a_n$ is little-O of $b_n$
 * $\displaystyle \lim_{n\to\infty}\frac{a_n}{b_n} = 0$