The Greeks produced great advancements in mathematics which are still used today. Some of them are mentioned below.
Euclid was known for the basic rules and terms of geometry. He wanted to prove that things were true by using logic and reason. Euclid's books begin with basic definitions of a point and a line and shapes, and then go on to use geometry to prove, for instance, that all right angles are equal, that you can draw a straight line between any two points, and that two things which are both equal to the same thing are also equal to each other.
Pythagoras was famous for his theorem A2 +B2 = C2 for a right triangle. Pythagoras also came up with the value of pie to calculate the circumference of a circle.
Archimedes discovered the physical law of displacement. The law of displacement is when an object moves the same volume of water as the object which is placed in it. Archimedes also used levers and pulleys to move heavy objects. He once launched a fully loaded ship all by himself. Archimedes also invented the Archimedes screw, which raises water up from rivers for the irrigation of fields. In addition to discoveries in math and physics, he also invented weapons to help the Greeks fight off Roman invasion. One of those weapons was the catapult. In 21 B.C. the Romans captured his city and killed him.
Parmenides watched an eclipse of the Moon in about 470 BC, and noticed that the Earth's shadow was curved. He worked out that if the shadow was curved, then the Earth must be round.
Hippocrates was a scientist of medicine; Hippocrates is called the Father of Western Medicine. Doctors still take the Hippocratic Oath today.
Aristarchus An astronomer and mathematician, Aristarchus was the first to put the sun at the center of the known universe rather than the Earth.
Phidias, or the great Phidias, was a Greek sculptor, painter and architect, who lived in the 5th century BC, and is commonly regarded as one of the greatest of all sculptors of Classical Greece.
Democritus was an Ancient Greek philosopher. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos.