Definition:Logical Not

The logical not or negation operator is a unary connective whose action is to reverse the truth value of the statement on which it operates.

$$\lnot p$$ is defined as: "$$p$$ is not true", or "It is not the case that $$p$$ is true".

Thus the statement $$\lnot p$$ is called the negation of $$p$$.

"$$\lnot p$$" is voiced "not $$p$$".

Different symbols that you may encounter that mean the same thing as $$\lnot p$$ are:
 * $$\sim p$$, where "$$\sim$$" is called the "tilde" sign;
 * $$- p$$;
 * $$\overline p$$.