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.
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imaginary unit
