HTML Entity for Empty Set (∅)
What You'll Learn
How to display the Empty Set (∅) in HTML using hexadecimal, decimal, named entity, and CSS escape methods. This character is U+2205 (EMPTY SET) in the Mathematical Operators block (U+2200–U+22FF)—the standard notation for a set with no elements in set theory, mathematics, and logic.
Render it with ∅, ∅, the named entity ∅, or CSS escape \2205. Compare with element-of (∈, ∈) when writing membership notation such as x ∉ S or ∅ ⊆ A.
⚡ Quick Reference — Empty Set
U+2205Mathematical Operators
∅Hexadecimal reference
∅Decimal reference
∅Standard in HTML
Name Value
──────────── ──────────
Unicode U+2205
Hex code ∅
HTML code ∅
Named entity ∅
CSS code \2205
Related U+2208 = Element of (∈ ∈); U+2209 = Not element ofComplete HTML Example
This example demonstrates the Empty Set (∅) using hexadecimal code, decimal HTML code, the named entity, and a CSS content escape:
<!DOCTYPE html>
<html>
<head>
<style>
#point:after{
content: "\2205";
}
</style>
</head>
<body>
<p>Empty Set using Hexadecimal: ∅</p>
<p>Empty Set using HTML Code: ∅</p>
<p>Empty Set using HTML Entity: ∅</p>
<p id="point">Empty Set using CSS Entity: </p>
</body>
</html>🌐 Browser Support
The Empty Set entity is universally supported in modern browsers:
👀 Live Preview
See the empty set (∅) in set-theory context and compared with element-of (∈):
∅ ∅ vs ∈ ∈🧠 How It Works
Hexadecimal Code
∅ uses the Unicode hexadecimal value 2205 to display the empty set symbol. The x prefix indicates hexadecimal format.
Decimal HTML Code
∅ uses the decimal Unicode value 8709 to display the same character.
Named Entity
∅ is the standard named entity for U+2205. It is readable and easy to remember in set-theory markup.
CSS Entity
\2205 is used in CSS stylesheets, particularly in the content property of pseudo-elements like ::before and ::after.
Same visual result
All four methods produce the empty set glyph: ∅. Unicode U+2205 in the Mathematical Operators block (U+2200–U+22FF).
Use Cases
The Empty Set (∅) commonly appears in:
Denote the unique set with no elements in definitions and proofs.
Math courses, textbooks, and tutorials on discrete math and logic.
Formal logic and proof writing with standard mathematical notation.
Type systems, databases, and APIs documenting empty collections.
Papers and preprints with correct set-theory symbols in HTML.
Unicode and entity reference pages for math operators.
💡 Best Practices
Do
- Use
∅for U+2205 in HTML set-theory content - Use math-friendly fonts for clear ∅ rendering
- Serve pages with UTF-8 (
<meta charset="utf-8">) - Add context when the symbol carries meaning (e.g. aria-label)
- Pair with
∈and subset symbols as needed
Don’t
- Use the letter O or zero as a substitute for ∅
- Confuse U+2205 (empty set) with unrelated lookalike characters
- Put CSS escape
\2205in HTML text nodes - Assume every font renders ∅ with the same stroke weight
- Mix entity styles randomly in one file
Key Takeaways
Three HTML references plus CSS all render ∅
∅ ∅ ∅For CSS stylesheets, use the escape in the content property
\2205Unicode U+2205 — Mathematical Operators empty set
∅ is the standard named entity
Element of is ∈ (∈, U+2208)
❓ Frequently Asked Questions
∅ (hex), ∅ (decimal), ∅ (named), or \2205 in CSS content. All produce ∅.U+2205 (EMPTY SET). Mathematical Operators block (U+2200–U+22FF). Hex 2205, decimal 8709.∅ is the HTML named entity for U+2205 (∅). Always include the semicolon: ∅.∅, ∅, or ∅) go directly in markup. The CSS escape \2205 is used in stylesheets, typically in the content property of pseudo-elements. Same visual result, different layers of the stack.Explore More HTML Entities!
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