# Algebra

- id: al-jabr
- original title: الكتاب المختصر في حساب الجبر والمقابلة / al-Kitāb al-mukhtaṣar fī ḥisāb al-jabr wa-l-muqābala
- author: al-Khwarizmi
- language: Arabic
- composed: c. 813–833, Baghdad
- field: mathematics

Al-Khwarizmi's compendium on solving equations by completion and balancing, written in Baghdad with al-Ma'mun's encouragement. The discipline it founded still carries the first noun of its title: al-jabr, algebra.

## The chain

- **1145** Arabic -> Latin, translation [attested]
  Robert of Chester (translator), Segovia
  The first Latin algebra, finished at Segovia in 'era 1183' of the Spanish calendar, which converts to 1145. The familiar title Liber algebrae et almucabola comes from a 1915 edition based on late copies, not from Robert's manuscripts.
  Evidence: Hughes 1989 (critical edition from the earliest manuscripts); Burnett 2004 (on the Robert of Chester and Robert of Ketton question)
- **c. 1150–1187** Arabic -> Latin, translation [attested]
  Gerard of Cremona (translator), Toledo
  Gerard's independent translation, undated in the manuscripts, made in Toledo before his death in 1187. It circulated alongside Robert's and was the version most algebraists used.
  Evidence: Lemay 1978; Burnett 2001

## Worth knowing

The moment algebra entered Latin is dated in a calendar nobody outside Iberia used. Robert of Chester's colophon says he finished at Segovia in 'era 1183', the Spanish era, which runs 38 years ahead of Anno Domini. The famous date 1145 is itself a conversion. And if Robert of Chester is the same man as Robert of Ketton, the same Englishman had translated the Qur'an into Latin two years before.

## Sources

- Hughes, Barnabas B. (1989). Robert of Chester's Latin Translation of al-Khwarizmi's al-Jabr: A New Critical Edition. Steiner Verlag.
- Toomer, G. J. (1973). al-Khwarizmi. Dictionary of Scientific Biography.

Confidence grades: attested (named in the medieval record or settled in scholarship), probable (standard view with real uncertainty), disputed (scholars disagree).