An Etymological Dictionary of Astronomy and Astrophysics

The symbol √ placed before a number or quantity to indicate the extraction of the square root. The value of a higher (the n-th) root is indicated by a raised positive digit (n) in front of the symbol, as in ³√ (cube root). The first known occurrence of this symbol was in the book Die Cross, published in 1525, by the German mathematician Christoff Rudolff.

See also: → radical; → symbol.