1. (n.) An ultimate indivisible particle of matter.

2. (n.) An ultimate particle of matter not necessarily indivisible; a molecule.

3. (n.) A constituent particle of matter, or a molecule supposed to be made up of subordinate particles.

4. (n.) The smallest particle of matter that can enter into combination; one of the elementary constituents of a molecule.

5. (n.) Anything extremely small; a particle; a whit.

6. (v. t.) To reduce to atoms.

Bohr atom Dirac atom I Lewis-Langmuir atom Thomson atom ace acid acidity agent air alkali alkalinity alloisomer anion antacid atomic model atomic particles atoms base biochemical bit brute matter building block cation chemical chemical element chromoisomer component compound constituent copolymer cubical atom dab dash dimer dole dot dram dribble driblet dwarf dyad earth electron element elementary particle elementary unit fabric farthing fire fleck flyspeck fragment fundamental particle gobbet grain granule groat hair handful heavy chemicals heptad hexad high polymer homopolymer hydracid hyle hypostasis inorganic chemical ion iota isobar isomer isotopic isobar jot labeled atom little little bit lota macromolecule material material world materiality matter medium meson metamer minim minimum minutiae mite modicum molecule monad monomer mote natural world nature neutral atom neutralizer no other nonacid none else normal atom nothing else nought beside nuclear atom nuclear isomer nuclear particle nuclide nutshell octad one one and only organic chemical ounce oxyacid particle pebble pentad physical world pinch pittance planetary shell plenum point polymer proton pseudoisomer quark radiation atom radical reagent recoil atom scruple shade shell smack smidgen smitch soupcon speck spice spoonful spot stripped atom stuff subshell substance substratum suggestion sulfacid suspicion tagged atom tangible tetrad the four elements thimbleful tincture tinge tiny bit tittle touch trace tracer tracer atom triad trifling amount trimer trivia unit unit of being valence shell water whit