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- The bottom element in lattice theory
- The bottom type in type theory
- A logical constant denoting "false" in logic
- Mixed radix decoding in the APL programming language
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: