Definition: A state i is an absorbing state if pij=1.
Definition: A state i is a transient state if there exists a state j that is reachable from i, but the state i is not reachable from state j.
Definition:If a state is not transient, it is called a recurrent state.
Definition:A state i is periodic with period k > 1 if k is the smallest number such that all paths leading from state i back to state i have a length that is a multiple of k. If a recurrent state is not periodic, it is referred to as aperiodic.
If all states in a chain are recurrent, aperiodic, and communicate with each other, the chain is said to be ergodic.
The importance of these concepts will become clear after the next two sections.