Initiation methods refer to the various techniques used to start a chemical reaction or process. Common initiation methods include thermal initiation, where heat is applied to trigger a reaction, and photoinitiation, which uses light to activate reactants. These methods are essential in fields like polymer chemistry and materials science. Another important initiation method is chemical initiation, where specific chemicals, known as initiators, are added to a reaction mixture to start the process. This is often seen in the production of polymers, such as polyethylene and polystyrene, where initiators help form long chains of molecules.