IMPORTANT: The angles are named vertex-point on leg-point on leg.
Angles are vertical if they share a vertex.
$\angle ABC$, $\angle ACD$, $\angle ADE$ and $\angle AEC$ are vertical.
Angles are vertically opposite if they are also opposite from each other.
$\angle ABC$ and $\angle ADE$ are vertically opposite, as are $\angle ACD$ and $\angle AEC$.
Similarly, asymptotes can be vertical, horizontal or slanted.
So, if angles can be vertical, can they be horizontal or slanted?