An Etymological Dictionary of Astronomy and Astrophysics

A nuclear reaction in which two or more atomic nuclei fuse into a single heavier nucleus by a collision of the interacting particles at extremely high temperatures.
Chains of thermonuclear reactions, such as the → proton-proton chain and the → CNO cycle, account for the energy radiated from the Sun and more massive stars.

See also: → thermo- + → nuclear; → reaction.