A catalyst is a substance that can accelerate a chemical reaction of another substance without itself undergoing a permanent chemical change.
(A catalyst; is; a substance that can accelerate a chemical reaction of another substance without itself undergoing a permanent chemical change) (a substance; can accelerate; a chemical reaction of another substance) (itself; undergoing; a permanent chemical change)
A catalyst a substance itself
is can accelerate undergoing
a substance that can accelerate a chemical reaction of another substance without itself undergoing a permanent chemical change
a chemical reaction of another substance
a permanent chemical change