Atom splitting, scientifically known as nuclear fission, is a term used to describe the process of breaking down the nucleus of an atom into two or more smaller nuclei. Synonyms for this process include nuclear disintegration, nuclear splitting, and nuclear cleavage. Another term that can be used in a more general sense is nuclear reaction, which encompasses both fission and fusion (the process of combining two atomic nuclei into a heavier nucleus). Additional synonyms for atom splitting include radiolysis, nuclear breakdown, and thermonuclear reaction. These terms all describe various forms of nuclear reactions that occur within the nucleus of an atom.