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- Archimedes: Topic Page287–212 B.C., Greek mathematician, physicist, and inventor. He is famous for his work in geometry (on the circle, sphere, cylinder, and parabola), physics, mechanics, and hydrostatics.
- Euclid (fl. 300 BCE): Topic PageGreek mathematician whose works, and the style in which they were presented, formed the basis for all mathematical thought and expression for the following 2,000 years (although they were not entirely without fault).
- Euclidean Geometry: Topic PageGeometry based on the definitions and axioms set out in Euclid's Elements. Book I starts out with 23 ‘definitions’ of the type ‘a point is that which has no part’ and ‘a line is a length without breadth’.
- Pi: Topic PageIn mathematics, the ratio of the circumference of a circle to its diameter.
- Ptolemy (fl. 2nd cent. CE): Topic Page(Claudius Ptolemaeus) celebrated Greco-Egyptian mathematician, astronomer, and geographer. He made his observations in Alexandria and was the last great astronomer of ancient times.

- Aristotle (384-322 BCE): Topic PageGreek philosopher, b. Stagira. He is sometimes called the Stagirite.
- Democritus (460-370 BCE): Topic PageAncient writers believed that Democritus was the student of Leucippus. They are associated together as the first philosophers to hypothesize that invisible material objects—atoms—make up the universe.
- Epicurus (341-270 BCE): Topic PageGreek philosopher, b. Samos; son of an Athenian colonist. He claimed to be self-taught, although tradition states that he was schooled in the systems of Plato and Democritus by his father and various philosophers.
- Plato (ca. 427-347 BCE): Topic PageGreek philosopher. Plato's teachings have been among the most influential in the history of Western civilization.
- Pythagoras (ca. 582-ca. 507 BCE): Topic PagePre-Socratic Greek philosopher, founder of the Pythagorean school.
- Socrates (469-399 BCE): Topic PageGreek philosopher of Athens. Famous for his view of philosophy as a pursuit proper and necessary to all intelligent men, he is one of the great examples of a man who lived by his principles even though they ultimately cost him his life.