(4th century BC)Educated in Athens by Platos students, Euclid taught geometry in Alexandria and founded a mathematics school there.
He wrote about optics, the heavens, the scale, the theory of numbers and also about music.
His work Stoicheia ("The Elements") is a text about plane geometry, whose methods are still partly used.
Euclid has also contributed through language, he has provided us with words such as triangle, quadrat, circle, problem, base, definition, axiom and parallel.
Of Euclids students was reputedly also king Ptolemy Soter, who was said to have difficulties in following his tutor.