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⊤

down tack

Down tack

⊤ is a formal “top” symbol: logic uses it for truth or a tautology, and lattice theory for the greatest element. Type theory can also use it for an always-true proposition.

Text symbol

Search it as: top symbol · ⊤ meaning · verum · lattice top · \top
Shows up in: Anything that takes text · its shape is whatever your font draws

What ⊤ means

It denotes truth, tautology, or the greatest element, depending on the notation. In logic, it can name verum (truth) or a tautology, a statement true in every case. Lattice theory studies ordered structures; there ⊤ marks the greatest element. Type theory can use it for an always-true proposition.

An APL note from 2000 records competing Bosworth and London names for tack symbols. APL is a programming language with its own mathematical notation.

Formal notation in logic, lattice theory, and type theory.

Don't confuse it with

⊥

Up Tack

Its bar is below the stem, giving it the inverted shape.

⊢

Right Tack

The bar projects right; in logic this turnstile marks derivability or a proof judgment.

Questions people ask

Why does ⊤ show as a box on some devices?

Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.

How to type ⊤

Windows (Word)

Alt+XType 22A4, then Alt+X to get ⊤.

Windows

Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).

macOS

Control+Command+SpaceOpen the character viewer and search “down tack”.

Linux

Ctrl+Shift+UType 22a4, then Enter or Space.

HTML

⊤

CSS

\22A4

LaTeX

In LaTeX math mode, enter `\top`.

Codes and encoding1 code points

HTML decimal

⊤

HTML hex

⊤

CSS content

content: "\22A4";

Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.

URL encoded

%E2%8A%A4

On screen

Code points

JS .length

UTF-8 bytes

A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.

Families this belongs to

Maths & numbers1,835 symbols

1️⃣📏📐✖️➕➖➗🟰♾️#️⃣*️⃣0️⃣