We only know this through citations of his works (titled On Numbers, On Geometrics, On Tangencies, On Mapping, and On Irrationals) in other writings, since most of Democritus's body of work did not survive the Middle Ages.
Ovo znamo radi citata u njegovih djela (O prirodi, O geometriji, O tangentama, O mapama, O iracionalnim brojevima) u drugim djelima, jer većima njegovih djela nije preživjela Srednji Vijek.