Euclid was a Greek mathematician who is famous for writing a series of 13 books called Elements about geometry and other mathematical concepts. His concepts and explanations of plane geometry, which take up approximately the first half of the Elements books, have been used as a means of teaching geometric concepts to beginning students for centuries. Some of his contributions also deal with number theory, solid geometry and mathematical deduction.
According to Infoplease, Euclid was a Greek mathematician who taught in Alexandria during the fourth century and made a number of different contributions to mathematics, especially pertaining to the field of plane geometry, which deals with flat two-dimensional objects and their properties. He also wrote about fields as diverse as solid geometry, arithmetic, number theory, and optics.
Euclid also contributed a methodology through which mathematics could be presented in a deductive way. This included bringing such words into the modern mathematical vocabulary as points, lines, assumptions and postulates. He was influential in developing the interplay of mathematics with logical proofs. Mathematics uses logic regularly and requires it to prove many of its different postulates. While the system devised by Euclid is no longer used in modern mathematics, it was crucial in its influence on the development of mathematics.