HTML Entity for Caution Sign (☡)
What You'll Learn
How to display the Caution Sign (☡) in HTML using numeric references and CSS escapes. This character is U+2621 (CAUTION SIGN) in the Miscellaneous Symbols block (U+2600–U+26FF), approved in Unicode 1.1 (1993). It was introduced by the Nicolas Bourbaki group of mathematicians and marks passages that are tricky on first reading or contain especially difficult arguments.
There is no named HTML entity for U+2621. Use ☡, ☡, or \2621 in CSS content. Do not confuse ☡ with the general Warning Sign (⚠, U+26A0) or the Radioactive Sign (☢, U+2622).
⚡ Quick Reference — Caution Sign
U+2621Miscellaneous Symbols block
☡Hexadecimal reference
☡Decimal reference
—None (use numeric refs)
Name Value
──────────── ──────────
Unicode U+2621
Hex code ☡
HTML code ☡
Named entity —
CSS code \2621Complete HTML Example
This example shows U+2621 using hexadecimal and decimal references plus a CSS content escape. There is no named HTML entity:
<!DOCTYPE html>
<html>
<head>
<style>
#point:after{
content: "\2621";
}
</style>
</head>
<body>
<p>Caution Sign using Hexa Decimal: ☡</p>
<p>Caution Sign using HTML Code: ☡</p>
<p id="point">Caution Sign using CSS Entity: </p>
</body>
</html>🌐 Browser Support
The Caution Sign entity is universally supported in all modern browsers:
👀 Live Preview
See the Caution Sign in mathematical and reference contexts:
🧠 How It Works
Hexadecimal Code
☡ uses the Unicode hexadecimal value 2621 to display the Caution Sign symbol.
Decimal HTML Code
☡ uses the decimal Unicode value 9761 to display the same character.
CSS Entity
\2621 is used in CSS stylesheets, particularly in the content property of pseudo-elements like ::before and ::after.
Same visual result
All three methods produce the Caution Sign glyph: ☡. Unicode U+2621 sits in the Miscellaneous Symbols block (U+2600–U+26FF).
Use Cases
The Caution Sign (☡) commonly appears in:
Marking difficult passages, tricky arguments, and proofs needing careful reading.
Bourbaki-style notation in algebra, analysis, and set theory textbooks.
Alerting readers to sections that need extra attention (not general safety warnings).
Mathematics tutorials, proofs, and problem sets with difficulty indicators.
Marking sections with non-obvious logic or edge cases.
Highlighting complex derivations or assumptions in scientific writing.
Pair with text or aria-label="difficult passage" for screen readers.
💡 Best Practices
Do
- Use
☡or☡for Bourbaki-style math caution - Place the symbol before passages that are tricky on first reading
- Add
aria-label="caution: difficult passage"when used decoratively - Choose fonts that support Miscellaneous Symbols (U+2600–U+26FF)
- Declare
<meta charset="utf-8">for reliable rendering
Don’t
- Use ☡ for general safety warnings (use ⚠ Warning Sign instead)
- Confuse ☡ with ☢ (Radioactive) or ☣ (Biohazard)
- Put CSS escape
\2621inside HTML text nodes - Rely on the symbol alone without accessible context
- Mix entity styles randomly in one file
Key Takeaways
Two HTML references both render ☡
☡ ☡For CSS stylesheets, use the escape in the content property
\2621U+2621 CAUTION SIGN — Bourbaki mathematics notation
Marks difficult or tricky passages in math texts
Not the same as ⚠ (Warning Sign) or ☢ (Radioactive)
❓ Frequently Asked Questions
☡ (hex), ☡ (decimal), or \2621 in CSS content. All produce ☡. There is no named HTML entity.U+2621 (CAUTION SIGN). Miscellaneous Symbols block (U+2600–U+26FF). Hex 2621, decimal 9761. Created by the Nicolas Bourbaki group for difficult mathematical passages.☡ or ☡) go directly in markup. The CSS escape \2621 is used in stylesheets, typically in the content property of pseudo-elements. Same visual result, different layers of the stack.☡, ☡, or \2621 in CSS. Do not confuse ☡ with ⚠ (Warning Sign) or ☢ (Radioactive Sign).Explore More HTML Entities!
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