tee (symbol)

{{Short description|Typographical symbol resembling a "T"}}

The tee (⊤, \top in LaTeX), also called down tack (as opposed to the up tack) or verum,{{Cite journal |last=Polkowski |first=Lech T. |date=2023 |title=Logic: Reference Book for Computer Scientists |url=http://dx.doi.org/10.1007/978-3-031-42034-4 |journal=Intelligent Systems Reference Library |volume=245 |pages=180 |doi=10.1007/978-3-031-42034-4 |isbn=978-3-031-42033-7 |issn=1868-4394|url-access=subscription }} 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.{{cite web |title=tautology {{!}} Definition & Facts |website=Encyclopedia Britannica |language=en |url=https://www.britannica.com/topic/tautology |access-date=2020-08-14}}{{cite web |title=Definition of TAUTOLOGY |language=en |website=www.merriam-webster.com |url=https://www.merriam-webster.com/dictionary/tautology |access-date=2020-08-14}}{{cite web |last=Weisstein |first=Eric W. |title=Tautology |language=en |website=mathworld.wolfram.com |url=https://mathworld.wolfram.com/Tautology.html |access-date=2020-08-14}} 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.