nuclear reaction

noun

1. reaction(def 8).

noun

1. a process in which the structure and energy content of an atomic nucleus are changed by interaction with another nucleus or particle

1. A process, such as fission, fusion, or radioactive decay, in which the structure of an atomic nucleus is altered through release of energy or mass or by being broken apart. See more at fission fusion.

A reaction that changes the number of protons or neutrons in the nucleus of an atom. There are several kinds of nuclear reactions, including the fragmentation of large nuclei into smaller ones (nuclear fission), the building up of small nuclei into larger ones (nuclear fusion), and changes begun by collisions with elementary particles or other nuclei (as in particle accelerators).