A generalized topology, $\mu$ on a set $X$ is a collection of subsets of $X$ s.t. $\varphi\in\mu$ and arbitrary unions of members of $\mu$ belong to $\mu$; and the ordered pair $(X, \mu)$ then stands for a generalized topological space.
A generalized topology (GT, for short) $\mu$ on a set $X$ is a collection of subsets of $X$ such that $\varphi\in\mu$ and arbitrary unions of members of $\mu$ belong to $\mu$; and the ordered pair $(X,\mu)$ then stands for a generalized topological space (abbreviated as GTS).