U+21D4\Leftrightarrow⇔⇔<mo>⇔</mo>Semantic identity and intent
Characters to distinguish
- ⇒ — Implies
Use ⇔ in the right format
Meaning and usage
Indicates that two statements imply each other and are logically equivalent.
Use it when both directions have been established.
Pronunciation: if and only if
Formula examples
n\text{ even}\Leftrightarrow n=2kHow to type If and Only If
- Windows
- Use Character Map or enter U+21D4 in a Unicode-aware app.
- macOS
- Open Character Viewer with Control–Command–Space and search by name.
- Microsoft Word
- Type \Leftrightarrow in an equation and press Space.
- iPhone and iPad
- Copy and paste ⇔, or use a math/LaTeX app. The standard iOS keyboard may not expose every mathematical symbol.
- Android
- Copy and paste ⇔, or use a math keyboard or LaTeX editor. Keyboard layouts vary by device and app.
- Google Docs
- For plain text, paste ⇔ or use Insert → Special characters. For structured math, use the equation editor and verify \Leftrightarrow.
- Excel
- Paste ⇔ into a cell or use Insert → Symbol when available. Ordinary cells preserve the character but do not interpret LaTeX commands.
Common mistakes
- Define the logical convention before using ⇔; proof, programming, and Boolean-algebra sources may assign different precedence or direction.
- For plain text, copy ⇔ as U+21D4; for structured equations, use \Leftrightarrow in math mode. A look-alike glyph or image can break search, accessibility, or parsing when the intended character is If and Only If.
When to use ⇔
- Use ⇔ in plain text when a Unicode character is appropriate and the destination preserves U+21D4.
- Use \Leftrightarrow in an equation editor when mathematical spacing or structure matters.
- Define the local meaning when If and Only If is used in logic, arrows with a field-specific convention.
Look-alikes and related characters
- ⇒ — Implies
Font and compatibility notes
Glyph shape can vary by font. Verify the code point after copying, and prefer LaTeX or MathML for structured equations.
Continue the workflow
From If and Only If to a finished equation
- Copy the characterUse ⇔ in plain text when Unicode is accepted.
- Choose a structured formatUse
\Leftrightarrowfor LaTeX or the MathML snippet for accessible web equations. - Edit or convertOpen the value in the editor or converter without retyping it.
Review and source notes
Quality tier: core
Last reviewed: 2026-07-26
Review method: Checked If and Only If against its Unicode identity, LaTeX representation, HTML serialization, MathML token, and copy-and-paste behavior.
Verified against: Unicode Standard, Unicode mathematical notation guidance, and established LaTeX/MathML syntax.
Reference sources
- The Unicode StandardUnicode Consortium — Character identity, encoding, names, and conformance.
- Unicode Character Code ChartsUnicode Consortium — Code points and official character charts.
- Unicode Technical Report #25: Unicode Support for MathematicsUnicode Consortium — Mathematical character usage, variants, and notation support.
- LaTeX Project DocumentationThe LaTeX Project — LaTeX syntax, authoring model, and official documentation links.
- MathML CoreW3C — Semantic web mathematics elements and browser behavior.
Frequently asked questions
What does the If and Only If symbol mean?
Indicates that two statements imply each other and are logically equivalent.
What is the LaTeX command for ⇔?
Use \Leftrightarrow in a compatible math environment.
Can I copy ⇔ as Unicode?
Yes. Use the copy button above to copy the Unicode character directly.