catalyst: a substance that changes the speed of a chemical reaction without affecting the yield or undergoing permanent chemical change*
As you can see NO (nitrogen monoxide) did not undergo a permanent change.
Thank you for your prompt response. I know the definition of catalyst, but I am having trouble figuring out how to find the catalyst in a reaction.
Sarah: If one started with NO, and ended with NO, it was unchanged in the reaction. NO is the catalyst.