Thermonuclear energies refer to the high levels of energy released during nuclear fusion reactions that take place inside stars like the Sun. Some synonyms for thermonuclear energies include fusion energy, atomic energy, nuclear energy, and plasma energy. These different phrases all refer to the same natural process, which involves the combination of atomic nuclei under extreme heat and pressure. Thermonuclear reactions are a vital source of power and heat in many applications, such as nuclear power plants and experimental fusion reactors. They are also the driving force behind the tremendous energy output of stars, which makes them essential for understanding the workings of the universe.