Definition:Little-O Notation/Real/Infinity/Definition 2

Definition
Let $f$ and $g$ be real-valued or complex-valued functions on a subset of $\R$ containing all sufficiently large real numbers. $f$ is little-o of $g$ as $x \to \infty$ :
 * $\forall \epsilon \in \R : \epsilon > 0 : \exists x_0 \in \R : \forall x \geq x_0 : |f(x)| \leq \epsilon \cdot |g(x)|$