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Before symbols, the words "roots" or "side" were commonly used for the square root of a number. Arab writers thought of a square number as growing out of a root, so Arabs often used the word *radix*, "extracting," or pulling out, the root. Latin writers thought of it as "finding" the latus, or side of a square.

Late medieval Latin writers turned radix into a single symbol R_{x}. This was used for more than one hundred years. The French writer Nicolas Chuquet (1484) sometimes used R_{x}^{2} for R_{x}, R_{x}^{3} and R_{x}^{4} for cube and fourth roots, respectively.

The symbol was introduced by Christoff Rudolff in 1525 in his book *Die Coss*. It is believed this symbol was used because it resembled a small *r* (*radix*) at the time. The cube and fourth roots were as shown below:

Cube Root | Fourth Root |

Rudolff's symbol was not immediately used. The letter *l* (latus, "side") was often used. For example the square root of 4 was *l*4 and the third root of 5 was *lc*5. By the seventeenth century, the square root symbol was being used regularly even though there were many ways the indices were written for higher roots.