Theaetetus (masanin lissafi)
Theaetetus na Athens  / ; Girka : Θεαίτητος _ _ _ _ _  ; c. 417 – ku. 369 BC),  watakila ɗa na ga Euphronius na Athens deme Sunium, ya kasance masanin lissafin Girka. Babban gudunmawarsa sun kasance a kan irrational lengths, wanda aka haɗa cikin Littafin X na  Euclid Elements da kuma tabbatar da cewa akwai regular convex polyhedra guda biyar.  Abokin Socrates da Plato ne, shi ne babban jigo a cikin tattaunawar eponymous Socratic dialogue.  na Plato.

Theaetetus, kamar Plato, ɗalibi ne ga masanin lissafin Girka Theodorus na Cyrene . Cyrene wata ƙasa ce mai albarka ta Girka a bakin tekun Arewacin Afirka, a cikin ƙasar Libiya a yau, a gabashin ƙarshen Tekun Sidra. Theodorus ya binciko ka'idar da ba za ta iya misaltuwa ba, kuma Theaetetus ya ci gaba da waɗancan karatun da ƙwazo; musamman, ya rarraba nau'ikan lambobi daban-daban bisa ga yadda aka bayyana su a matsayin tushen murabba'i. An gabatar da wannan ka'idar dalla-dalla a cikin Littafin X na Abubuwan Euclid.

Theaetetus ɗaya ne daga cikin ƴan tsirarun masana lissafin Girka waɗanda a zahiri asalin 'yan kasar Athens ne. Yawancin malaman lissafi na Girka na zamanin da sun fito ne daga garuruwan Girka daban daban a kusa da gabar tekun Ionian, Bahar Bahar Rum da kuma daukakin bakin tekun Bahar Rum.

Babu shakka ya yi kama da Socrates ta hancinsa da kumburewar idanunsa. Wannan da kuma mafi yawan abin da aka sani game da shi ya fito ne daga Plato, wanda ya sanyawa wani labarinsa sunansa, Theaetetus. Da alama ya mutu daga raunuka da ciwon daji a hanyarsa ta komawa gida bayan yaƙi a yaƙin Atina a Koranti, yanzu ana zaton yakin ya faru a shekara ta 369 BC; wasu malaman suna jayayya akan 391 BC a matsayin ranar mutuwarsa, ranar yaƙin farko a Koranti. 

Akwai wani rami Theaetetus on the Moon da aka sanya wa sunansa.

Duba kuma 

 Jerin masu magana a cikin tattaunawar Plato

Manazarta

Hanyoyin haɗi na waje 

 Tattaunawar Gudunmawar Theaetetus ga Abubuwan Euclid
 

Matattun 369 BC