In chemistry or biology a substance that accelerates the rate of a chemical reaction but is otherwise unconsumed by the reaction (see also catalysis). A catalyst participates in the reaction, but is neither a chemical reactant or a chemical product of the net reaction.
Generally, catalysts work by providing a lower energy pathway for the overall reaction to occur. This usually occurs by the reaction of the catalyst with one or more reactants to form a stable intermediate that subsequently reacts to form the final reaction product and regenerate the catalyst.
The following is a typical catalytic reaction scheme, where C represents the catalyst:
A + C -> AC (1)
B + AC -> AB + C (2)
Note that while the catalyst (C) is consumed by reaction 1, it is subsequently produced by reaction 2, so for the overall reaction:
A + B + C -> AB + C
the catalyst is neither consumed nor produced.
Enzymes are bio-catalysts.
Use of the term in a broader cultural sense is in rough analogy to the sense described here and to the process described as catalysis.