What is the term for a substance that accelerates a chemical reaction?

A substance that accelerates a chemical reaction is known as a catalyst. Catalysts work by lowering the activation energy required for a reaction to occur, allowing the reactants to convert into products more efficiently and at a faster rate. They do not undergo any permanent chemical change themselves during the reaction, meaning they can be used repeatedly.

The other terms listed refer to different concepts in chemistry. An inhibitor, for example, slows down a chemical reaction rather than promoting it. A reactant is a substance that undergoes change during the reaction, while a product is the substance formed at the end of a reaction after the reactants have been transformed. Thus, a catalyst distinctly serves the role of enhancing the rate of reaction, making it the correct answer.