Low-Link Value

The low-link value low[v] is the smallest discovery time reachable from the subtree rooted at $v$. In other words: low[v] is the earliest vertex you can reach from $v$ using tree edges going down and at most one back edge going up. If low[v] = disc[v], then no back edges escape the subtree of $v$.

This means $v$ is isolated unless its parent edge is the only connection. This condition identifies bridges and articulation points.