# Algebra, restoration, and strength

It’s well-known that the word *algebra* comes from Arabic, but pursuing the origin in more detail reveals some interesting connections. The term comes from Persian mathematician Muhammad ibn Musa al-Khwarizmi, who made numerous contributions to mathematics during the Golden Age of Islamic Golden Age of the 9th and 10th centuries, and whose surname gives us the word *algorithm*.

The word comes from the title of a mathematical treatise by al-Khwarizmi entitled ٱلْكِتَاب ٱلْمُخْتَصَر فِي حِسَاب ٱلْجَبْر وَٱلْمُقَابَلَة (al-Kitāb al-Mukhtaṣar fī Ḥisāb al-Jabr wal-Muqābalah), or *The Compendious Book on Calculation by Restoration and Balancing*. The root *jabar* meant “to restore” or “to set a bone”, and still has that sense in modern Arabic.

al-Khwarizmi meant restoration in the following sense. Consider the equation $$x - 1 = 3.$$ In order to resolve this equation, one can move the $-1$ from the left to the right side by adding $ +1 $ to both sides, thus “restoring” the natural order of the equation.

The same root exists in Hebrew for words having to do with strength (setting a broken bone means restoring its strength, after all). Thus we have the words גבר (*gever*) *man* (particularly connoting a strong man) and גיבור (*gibur*) *hero*. There’s another word for man, איש (*ish*) referring to men or people more generally. The biblical name גבריאל (Gabriel) has the same origin, literally meaning *God is my strength*.