A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions.

• The neutron-fission chain reaction: a neutron plus a fissionable atom causes a fission resulting in a larger number of neutrons than was consumed in the initial reaction.
• Chemical reactions, where a product of a reaction is itself a reactive particle which can cause more similar reactions. For example, every step of H₂ + Cl₂ chain reaction consumes one molecule of H₂ or Cl₂, one free radical H· or Cl· producing one HCl molecule and another free radical.
• Electron avalanche process: Collisions of free electrons in a strong electric field forming "new" electrons to undergo the same process in successive cycles.

See also

• Nuclear chain reaction
• Polymerase chain reaction
• Markov chain
• Chain letter

Chemical kinetics

Reacció en cadena | Řetězová reakce | Kettenreaktion | Reacción en cadena | Réaction en chaîne | Верижна реакција | Kettingreactie | Reakcja łańcuchowa | Reacção em cadeia | Цепные реакции | Kedjereaktion