Catalysis is the change in
rate of a chemical reaction due to the participation of a substance
called a catalyst. Unlike other reagents that participate in the
chemical reaction, a catalyst is not consumed by the reaction
itself. A catalyst may participate in multiple chemical
transformations. Catalysts that speed the reaction are called
positive catalysts. Substances that slow a catalyst's effect in a
chemical reaction are called inhibitors. Substances that increase
the activity of catalysts are called promoters, and substances that
deactivate catalysts are called catalytic poisons.