Update markov_chains_II.md (#565)

lectures/markov_chains_II.md

@@ -58,7 +58,7 @@ import numpy as np
 
 To explain irreducibility, let's take $P$ to be a fixed stochastic matrix.
 
-State $x$ is called **accessible** (or **reachable**) from state $y$ if $P^t(x,y)>0$ for some integer $t\ge 0$. 
+State $y$ is called **accessible** (or **reachable**) from state $x$ if $P^t(x,y)>0$ for some integer $t\ge 0$. 
 
 Two states, $x$ and $y$, are said to **communicate** if $x$ and $y$ are accessible from each other.