text: The word "algebra" is named after the Arabic word "al-jabr" from the title of the book al-Kitāb al-muḫtaṣar fī ḥisāb al-ğabr wa-l-muqābala, meaning The book of Summary Concerning Calculating by Transposition and Reduction, a book written by the Persian mathematician Muḥammad ibn Mūsā al-Ḵwārizmī in 820. The word al-jabr means "reunion". Al-Khwarizmi is often considered the "father of algebra" (though that title is also given to Diophantus), as much of his works on reduction are still in use today. Another Persian mathematician Omar Khayyam developed algebraic geometry and found the general geometric solution of the cubic equation.