That is, 
is the reflexive, transitive closure of 
. We say that I 
J if the ID J follows from the ID I in zero or more moves.
is the reflexive, transitive closure of . We say that I J if the ID J follows from the ID I in zero or more moves.
( Note : subscript M can be dropped when the particular PDA M is understood. )
Language accepted by a PDA M
There are two alternative definiton of acceptance as given below.
1. Acceptance by final state :
Consider the PDA 
. Informally, the PDA M is said to accept its input 
by final state if it enters any final state in zero or more moves after reading its entire input, starting in the start configuration on input .