Imaginary Unit

The imaginary number , i.e., the square root of . The imaginary unit is denoted and commonly referred to as "i." Although there are two possible square roots of any number, the square roots of a negative number cannot be distinguished until one of the two is defined as the imaginary unit, at which point  and  can then be distinguished. Since either choice is possible, there is no ambiguity in defining  as "the" square root of . In the Wolfram Language, the imaginary unit is implemented as I.