(c.800-847)

Mathematician, astronomer, geographer, born in Baghdad around 800 AD. He was the founder of several branches and basic concepts of mathematics. He introduced algebra and Indian/ Arabic numerals, and the words “algebra” and “algorithm”, to Europe in the 12th century.

Al-Khwarizmi‘s most important and famous work, written in 830, is fi Hisab al-jabr w’al-muqabala. (On Calculation by Completion and Balancing). Here is where the word “algebra” comes from. In this book he gives a complete solution to all possible types of quadratic equations. The book contains sections on calculating areas and volumes of geometric figures and on the use of algebra to solve inheritance problems according to proportions prescribed by Islamic law. He perfected the geometric representation of conic sections and developed the calculus of two errors, which practically led him to the concept of differentiation.

Al-Khwarizmi reintroduced the Indian system of numerals (now generally known as Arabic numerals), developed several arithmetical procedures, explained the numeral zero, and developed the decimal system including operations on fractions.

He wrote a book on astronomy, and compiled a set of astronomical tables (zij). In geography he revised Ptolemy's map of the world. His other contributions include original works related to clocks, sundials and astrolabes. He also assisted in the construction of a world map for al-Ma'mun and participated in a project to determine the circumference of the Earth, which had long been known to be spherical, by measuring the length of a degree of a meridian through the plain of Sinjar in Iraq.

Several of his books were translated into Latin in the early 12th century. Kitab al-Jam'a wal- Tafreeq bil Hisab al-Hindi was lost in Arabic, but survived in a Latin translation. His book on algebra was also translated into Latin in the 12th century, and it was this translation which introduced this new science to the West. He astronomical tables were also translated into European languages and, later, into Chinese.

Several of his books were the standard university textbooks till the 16th century. His approach was systematic and logical, and he was able to bring together the existing knowledge on various branches of science, particularly mathematics, but also enriched it through his original contribution.