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  • Sign[ x ] gives -1, 0 or 1 depending on whether x is negative, zero, or positive.
  • For non-zero complex numbers z, Sign[ z ] is defined as z /Abs[ z ].
  • Sign tries simple transformations in trying to determine the sign of symbolic expressions.
  • You can define values for Sign[ expr ] which are used when expr, and linear combinations involving it, appear in Sign, as well as functions like Positive and Negative.
  • For exact numeric quantities, Sign internally uses numerical approximations to establish its result. This process can be affected by the setting of the global variable $MaxExtraPrecision.
  • See the Mathematica book: Section 3.2.2.
  • See also: Abs, Positive, Negative, NonNegative.