1) Like a quark 2) Like elementary particles 3) Like quarks 4) Matter 5) Substance 
Term applied to phenomena occurring within the atom, and to particles therein.
Pertaining to particles making up the intra-atomic structure; e.g., protons, electrons, neutrons. ... (05 Mar 2000) ... 
Type: Term Pronunciation: sŭb′ă-tom′ik Definitions: 1. Pertaining to particles making up the intraatomic structure; protons, electrons, neutrons.
[adj] - of or relating to constituents of the atom or forces within the atom 2. [adj] - of dimensions smaller than atomic dimensions
adjective of dimensions smaller than atomic dimensions
of or pertaining to a process that occurs within an atom. · noting or pertaining to a particle or particles contained in an atom, as electrons, protons, or neutrons.