Fraternally oriented digraph

Fraternally oriented digraph --- братски ориентированный граф.

A digraph [math]\displaystyle{ D }[/math] is called a fraternal orientation of [math]\displaystyle{ G_{D} }[/math] if [math]\displaystyle{ (u,w) \in A(D) }[/math] and [math]\displaystyle{ (v,w) \in A(D) }[/math] implies [math]\displaystyle{ (u,v) \in A(D) }[/math] or [math]\displaystyle{ (v,u) \in A(D) }[/math]. If [math]\displaystyle{ D }[/math] is a fraternal orientation of [math]\displaystyle{ G_{D} }[/math], we will say that [math]\displaystyle{ D }[/math] is a fraternally oriented digraph, [math]\displaystyle{ G }[/math] is fraternally orientable if it admits a fraternal orientation.