Extremely small particles--electrons, protons, and neutrons--that make up the internal structure of atoms.

Particles which are smaller than an atom. Examples include the electron, proton, and neutron.

Particles that make up an atom, i.e., electron and photon.

Fundamental components of matter such as electrons or protons.

The three kinds of particles that make up atoms: protons, neutrons, and electrons.

Protons, neutrons, and electrons are particles that make up the atom (p.33-38).