Definition:Little-O Notation/Real/Infinity

Definition
Let $f$ and $g$ be real-valued or complex-valued functions on a subset of $\R$ containing all sufficiently large real numbers.

Definition 2
This is denoted:
 * $f = o \left({g}\right)\qquad(x\to\infty)$

This statement is voiced $f$ is little-o of $g$ or simply $f$ is little-o $g$.

Also see

 * Equivalence of Definitions of Little-O Notation for Real Functions