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.

Euclid (lived c. 300 B.C.) is remembered as one of the greatest mathematicians in the world. Historians believe that Euclid probably studied at Athens under students of Greek philosopher Plato (c. 428–348 or 347 B.C.) before he founded a school of mathematics in Alexandria, Egypt, during the reign of Ptolemy I (?–283 B.C.). Euclid is best known for his work titled *Elements,* a thirteen-volume textbook on the principles of mathematics. They include treatises on plane geometry (a branch of geometry dealing with plane figures), proportion (the relationship among parts), astronomy (the study of stars, planets, and heavenly bodies), and music. Although no one knows if all of the work in *Elements* was Euclid's or if he compiled the mathematical knowledge of his colleagues (such as Eudoxus), the work formed an important part of mathematics for 2,000 years. Even today, modified versions of the first few books of *Elements* are still used to teach plane geometry.

**Further Information:** Baker, Rosalie F., and Charles F. Baker III. *Ancient Greeks: Creating the Classical Tradition.* New York: Oxford University Press, 1997, p. 191; *Euclid's Elements.* [Online] Available http://aleph0.clarku.edu/~djoyce/java/elements/elements.html, November 8, 2000; Young, Robyn V., ed. *Notable Mathematicians: From Ancient Times to the Present.* Detroit: Gale, 1998.