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Not (!, ¬)

is the logical NOT function. It gives False if expr is True, and True if it is False.
  • Not gives symbolic results when necessary, applying various simplification rules to them.
  • If you are using Mathematica with a text-based front end, then you cannot use the notation !expr for Not[expr] if it appears at the very beginning of a line. In this case, !expr is interpreted as a shell escape.  »
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