a particle smaller than an atom; a component of the atom. (see electron, proton, neutron)
Although an atom is the smallest complete piece of an element, the atom itself is made up of even smaller components known as subatomic particles. The three subatomic particles in atoms are protons, electrons, and neutrons. Elements are defined by the number of protons in their atoms.
the constituent parts of the atom, such as the electron, proton, neutron, etc.