In terms, atom, from the Greek atomos “uncutable”, possibly from the Egyptian god Atum, the original "land" mass (or land god) that arose from the mythical watery Nun or chaos of beginning (see: Atoms and Atum, refers to any bound state of protons, neutrons, and electrons, which come in 92 naturally occurring varieties, called "elements" depending upon the number of protons in its core or "nucleus".
The following are related quotes:
- “We see changes in things because of the rearrangement of atoms, but atoms themselves are eternal. Words such as ‘nothing’, ‘the void’, and ‘the infinite’ describe space. Individual atoms are describable as ‘not nothing’, ‘being’, and ‘the compact’. There is no void in atoms, so they cannot be divided. I hold the same view as Leucippus regarding atoms and space: atoms are always in motion in space.”
- — Democritus (c.420BC), Source; Rex Pay fragment #48 
- “Nothing exists except atoms and empty space; everything else is opinion.”
- — Democritus (c.420BC), Source; Rex Pay fragment #49 
- “It is called the ‘atom’ not because it is the smallest thing, but because it cannot be cut, since it cannot be affected and contains no void.”
- — Eusebius (c.313), Praeparatio Evangelica (§: XIV.14.5) 
- “If, in some cataclysm, all scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or atomic fact, or whatever you wish to call it) that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence you will see an enormous amount of information about the world, if just a little imagination and thinking are applied.”
- Atoms and Atum (WikiFoundry subdomain) – Hmolpedia 2020.
- [Pay, Rex. (2005). “Democritus”, HumanisticTexts.org]
- Taylor, C.C.W. (1999). The Atomists: Leucippus and Democritus: Fragments: a Text and Translation with a Commentary by C.C.W. Taylor (pg. 79). University of Toronto Press.
- Feynman time capsule wisdom (WikiFoundry subdomain) – Hmolpedia 2020.