1. a theory of the structure of the atom
(hypernym) scientific theory
(hyponym) Bohr theory
(part-holonym) nuclear physics, atomic physics, nucleonics
2. (chemistry) any theory in which all matter is composed of tiny discrete finite indivisible indestructible particles; "the ancient Greek philosophers Democritus and Epicurus held atomic theories of the universe"
(synonym) atomism, atomist theory, atomistic theory
(classification) chemistry, chemical science