¬ is the symbol for negation.
is the symbol for "therefore the conclusion is".
A letter representing a premise must follow ¬; example ¬Q or ¬S or ¬X. ¬Q= not a queen or ¬S= not silly, or ¬X = not X-Ray.
⊥ is not a logic operator, neither ⊥ is T. In math ⊥ means perpendicular.
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