Let $(X_n)_{n\ge 0}$ be a Markov Chain. Then the hitting time for a subset $A$ of $I$ (the indexing set) is the random variable:
This can be thought of as the time before the chain is first in a state that is a member of $A$
Wite $h_i^A$ for the probability that, starting from $i\in I$ the chain ever hits the set A: