A chain reaction is a reaction in which one of the agents necessary to the reaction is itself produced by the reaction, thus causing additional reactions.
- The neutron-fission chain reaction, a neutron plus a fissionable atom causes a fission resulting in a number of neutrons which in turn cause other fissions.
- Chemical chain reactions, where large molecules (e.g., plastic polymers, nucleic acids) are products.
See also: nuclear chain reaction
, polymerase chain reaction