Full Idea
Some substances are irregular, others hook-shaped, other concave, other convex, others provided with innumerable other differences.
Gist of Idea
Atoms are irregular, hooked, concave, convex, and many other shapes
Source
report of Democritus (fragments/reports [c.431 BCE], A037) by Aristotle - On Democritus (frag)
Book Reference
Democritus: 'Early Greek Phil VII: Democritus', ed/tr. Laks,A/Most,G [Harvard Loeb 2016], p.89
A Reaction
[quoted in Simplicius, Commentary on Aristotle's On the Heavens] 'Substance' here means a fundamental object, which for Democritus is an undividable atom.