A chain reaction is a sequence of single nuclear reactions, each of which is caused by a particle that appeared as a reaction product at the previous step of the sequence. An example of a nuclear chain reaction is a chain reaction of fission of nuclei of heavy elements, in which the majority of fission events are initiated by neutrons obtained during nuclear fission in the previous generation.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.