T-Tough graph

[math]\displaystyle{ t }[/math]-Tough graph --- [math]\displaystyle{ t }[/math]-жесткий граф.

A graph is [math]\displaystyle{ t }[/math]-tough, if the number of components of [math]\displaystyle{ G \setminus S }[/math] is at most [math]\displaystyle{ |S|/t }[/math] for every cutset [math]\displaystyle{ S \subseteq V(G) }[/math].

In particular, a graph [math]\displaystyle{ G }[/math] is called 1-tough, if [math]\displaystyle{ \omega(G - S) \leq |S| }[/math] for every set [math]\displaystyle{ S }[/math] of some vertices of [math]\displaystyle{ G }[/math] satisfying [math]\displaystyle{ \omega(G - S) \gt 1 }[/math], where [math]\displaystyle{ \omega(G - S) }[/math] denotes the number of components of [math]\displaystyle{ G - S }[/math].