Euclid, a Greek mathematician, lived in Alexandria at the time of Ptolemy I and did his most significant work in approximately 300 BCE. The biographical tradition concerning Euclid is scant, and on the main, unreliable. His major surviving work is his *Elements of Geometry*; other less important treatises on mathematics and optics are also extant, although several of works of his that are mentioned in ancient sources have not survived to the present. A long commentary on the *Elements* by Proclus, a Platonic philosopher, confirms a probable association of Euclid in his early career (possibly as a student) with the Platonic academy in Athens.

Euclid`s *Elements* has set down the basic principles of plane geometry as it has been studied from the Greeks through the present and he is often referred to as the `Father of Geometry.`

Though he is known as the "Father of Geometry," not much is know about Euclid's life. Born around 322 BC, what historians do know about him is mostly garnered from writings from historical figures referring to him after his death (estimated to be around 275 BC). While no physical description or likeness has remained, his theories and mathematical proofs have stood the test of time. Though originally published without an author's name or credit, his work *Elements* is considered "one of the most influential works in the history of mathematics, serving as the main textbook for teaching mathematics (especially geometry) from the time of its publication until the late 19th or early 20th century." Over twenty-three centuries after its original publication, his treatises of geometrical theories remain not only in tact, but a basis for mathematics.

**Further Reading**