Contradiction symbol (⊥, ↯) in LaTeX

There is no single standard contradiction symbol. \bot (falsum) is the most portable and is what logicians use. The clashing double arrows are a common classroom convention. Lightning bolts need extra packages and do not render in KaTeX.

All ways to write it

Command	Use	Package
`\bot`	falsum / up tack ⊥, the standard choice	none
`\Rightarrow\Leftarrow`	clashing arrows ⇒⇐	none
`\lightning`	lightning bolt ↯	stmaryrdnot in KaTeX
`\blitza`	lightning bolt	marvosymnot in KaTeX

Commands marked with a package need that \usepackage line in a LaTeX document. “Not in KaTeX” means the command will not render in KaTeX- or MathJax-based tools such as Markdown previews, Jupyter and Confluence math apps; use one of the other forms there.

Example

\sqrt{2} = \tfrac{p}{q} \text{ in lowest terms} \implies 2 \mid p \text{ and } 2 \mid q \quad \bot

The classic irrationality argument ending in a contradiction.

Questions

Which contradiction symbol works in Confluence or Markdown?

\bot and \Rightarrow\Leftarrow. The lightning bolts come from stmaryrd and marvosym, which KaTeX does not include.

Related symbols

Therefore ∴ \therefore
End of proof ∎ \blacksquare
Implies ⟹ \implies

Using contradiction in Confluence

Confluence Cloud has no built-in LaTeX. With LaTeX Math for Confluence you add a math macro to any page, type \bot and it renders inline or as a block, with a live preview while you edit. The app uses KaTeX, so pick one of the commands above that is not marked “not in KaTeX”.