A catalyst increases the rate of a particular reaction without itself being used up. A catalyst can be added to a reaction and then be recovered and reused after the reaction occurs. The process or action by which a catalyst increases the reaction rate is called catalysis. The study of reaction rates and how they change when manipulated experimentally is called kinetics.

The term catalysis was proposed in 1835 by the Swedish chemist Jöns Berzelius (1779-1848). The term comes from the Greek words kata meaning down and lyein meaning loosen. Berzelius explained that by the term catalysis he meant "the property of exerting on other bodies an action which is very different from chemical affinity. By means of this action, they produce decomposition in bodies, and form new compounds into the composition of which they do not enter."

Most chemical reactions occur as...