Tee (symbol)

The tee (⊤, \top in LaTeX), also called down tack (as opposed to the up tack) or verum,^[1] is a symbol used to represent:

The top element in lattice theory.
The truth value of being true in logic, or a sentence (e.g., formula in propositional calculus) which is unconditionally true.^[2]^[3]^[4] By definition, every tautology is logically equivalent to the verum.
The top type in type theory.
Mixed radix encoding in the APL programming language.
A lowered phonic in the International Phonetic Alphabet and phonetics. In this usage, it is usually written under the primary IPA symbol.

A similar-looking superscript T may be used to mean the transpose of a matrix.

Encoding

In Unicode, the tee character is encoded as U+22A4 ⊤ DOWN TACK (&DownTee;, &top;).^[5] The symbol is encoded in LaTeX as \top.

A large variant is encoded as U+27D9 ⟙ LARGE DOWN TACK in the Unicode block Miscellaneous Mathematical Symbols-A.

^ Polkowski, Lech T. (2023). "Logic: Reference Book for Computer Scientists". Intelligent Systems Reference Library. 245: 180. doi:10.1007/978-3-031-42034-4. ISBN 978-3-031-42033-7. ISSN 1868-4394.
^ "tautology | Definition & Facts". Encyclopedia Britannica. Retrieved 2020-08-14.
^ "Definition of TAUTOLOGY". www.merriam-webster.com. Retrieved 2020-08-14.
^ Weisstein, Eric W. "Tautology". mathworld.wolfram.com. Retrieved 2020-08-14.
^ "Mathematical Operators – Unicode" (PDF). Retrieved 2013-07-20.

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