A unary logical connective, denoted

\begin{equation*} \lnot P \qor \sim P \qor \bar{P} \qor !P \end{equation*}

and read

“not \(P\)”,

that is true if and only if

\(P\) is false.

Note. \(\lnot \lnot P \equiv P\).

[1, Sec. 0.2], [2, Sec. 5.1]

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