This article needs additional citations for verification. (May 2014) (Learn how and when to remove this template message)
- The truth value 'false', or a logical constant denoting a proposition in logic that is always false (often called "falsum" or "absurdum").
- The bottom element in lattice theory, which also represents absurdum when used for logical semantics
- The bottom type in type theory, which also represents absurdum under the Curry–Howard correspondence
as well as
The glyph of the up tack appears as an upside-down tee symbol, and as such is sometimes called eet (the word "tee" in reverse). Tee plays a complementary or dual role in many of these theories.
The similar-looking perpendicular symbol (⟂,
\perp in LaTeX, U+27C2 in Unicode) is a binary relation symbol used to represent:
- Perpendicularity of lines in geometry
- Orthogonality in linear algebra
- Independence of random variables in probability theory
- Comparability in order theory
- Coprimality in number theory