Show Summary Details

Page of

Printed from Oxford Classical Dictionary. Under the terms of the licence agreement, an individual user may print out a single article for personal use (for details see Privacy Policy and Legal Notice).

date: 01 February 2023


, of Athens, geometer, c. 415–369 bce


, of Athens, geometer, c. 415–369 bce
  • Wilbur R. Knorr
  •  and Reviel Netz


Theaetetus (c. 415–369 bce) of Athens, geometer, initiated the special definitions and theory of irrational lines fundamental for book 10 of Euclid's Elements (cf. Eudemus, cited by Pappus, ed. Junge and Thomson, 63–4); one infers that he formulated a proportion theory based on the Euclidean division (anthyphairesis) and perhaps also set out the associated number theory of Elements, book 7.


  • Science, Technology, and Medicine

You do not currently have access to this article


Please login to access the full content.


Access to the full content requires a subscription