A substance that speeds up a chemical reaction is called a "catalyst." Catalysts lower the activation energy required for a reaction to occur, thereby increasing the reaction rate without being consumed in the process. This means that they can be used repeatedly in chemical reactions. Catalysts are crucial in various industrial processes, such as the production of fertilizers, plastics, and fuels. They are also significant in biological systems; enzymes serve as natural catalysts that facilitate biochemical reactions necessary for life. Understanding catalysts is essential in fields like chemistry, biochemistry, and environmental science.