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  • ! expr is the logical NOT function. It gives False if expr is True, and True if it is False.
  • Not[ expr ] can be input in StandardForm and InputForm as ¬expr. The character ¬ can be entered as !, not or \[Not].
  • Not gives symbolic results when necessary, and applies 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.
  • See the Mathematica book: Section 1.5.6.
  • See also: LogicalExpand.

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