Empty set (∅) is the Unicode character at U+2205 in Mathematical Operators. Official name: EMPTY SET. It denotes a set with no elements — read “the empty set,” as in A = ∅.
Remember
Character ∅
Unicode U+2205
Named entity ∅
Aliases ∅ · ∅
Hex entity ∅
Decimal ∅
CSS escape \2205
Not the same Ø (Oslash) · {} · 0
Prefer ∅ in HTML markup. You can also use ∅ / ∅, or type ∅ in a UTF-8 document.
Built with Named: ∅
Built with Hex: ∅
Built with Decimal: ∅
Built with CSS: ∅
Typed: ∅
Equation: A = ∅
How It Works
1. Named:∅ is the preferred HTML5 name for U+2205 → ∅.
2. Hex:∅ inserts the same code point. Same visual as named.
3. Decimal: same code point as 8709 → ∅.
4. CSS: use \2205 in content (not an HTML entity). #point::after appends ∅.
5. Typed: paste ∅ in a UTF-8 document, or write an equation like A = ∅.
Pitfalls & Tips
Common mistakes when working with Empty Set.
Name
Prefer ∅
∅ is the clearest named form. ∅ and ∅ are valid aliases for the same glyph.
Ø
Not Latin O with stroke
Ø (Ø, U+00D8) looks similar but is a letter, not the empty-set operator. Prefer ∅ in math.
{}
Braces are notation, not the glyph
Writing {} can mean an empty set in set-builder syntax, but it is not Unicode U+2205. Use ∅ for the ∅ symbol.
CSS vs HTML
Do not mix escapes
\2205 belongs in CSS strings. ∅ / ∅ / ∅ belong in HTML.
Fonts
Math font coverage
Some fonts omit Mathematical Operators. Prefer a font with solid math coverage for set notation.
a11y
Add accessible text
Screen readers may not expand ∅ clearly. Prefer full phrases nearby (for example “A equals the empty set”) when the meaning matters.
Semicolon
End references
Always finish entities with ; — write ∅, not &empty.
Compatibility
Browser Support
Empty set (U+2205) and its entity forms (∅, ∅, ∅, CSS \\2205) are supported in all mainstream browsers. Visible glyphs depend on Mathematical Operators font coverage.
✓ Universal support
Empty Set (∅)
Encode with named, hex, decimal, CSS escape, or type the character — same code point everywhere encoding is supported.
100%Browser coverage
Google ChromeSupported
Yes
Microsoft EdgeSupported
Yes
Mozilla FirefoxSupported
Yes
Apple SafariSupported
Yes
OperaSupported
Yes
Internet ExplorerAll versions
Yes
U+2205 / ∅Full support
Bottom line: Prefer ∅ in HTML. Use ∅ / ∅ when numeric form is required, and \\2205 only inside CSS content.
Remember
Key Takeaways
Unicode: empty set is U+2205 (decimal 8709) — glyph ∅.
Use ∅ (named), ∅ (hex), ∅ (decimal), type ∅ directly in UTF-8, or the CSS escape \2205 in content. Aliases ∅ and ∅ also resolve to U+2205.
U+2205 (EMPTY SET). Hex 2205, decimal 8709. It belongs to the Mathematical Operators block (U+2200–U+22FF).
Yes. ∅ is the preferred readable named entity for U+2205. ∅ and ∅ are valid HTML5 aliases for the same character.
Use it for the empty set in math, logic, and CS docs (for example A = ∅). Prefer prose like “the empty set” nearby when accessibility matters. Do not use Ø (O with stroke) or 0 as a substitute.
HTML entities (∅, ∅, or ∅) go in markup. The CSS escape \2205 goes in stylesheet strings (usually content on ::before/::after).
No. U+2205 is ∅ (empty set). U+00D8 is Ø (Latin capital O with stroke). {} can write an empty set in set-builder notation, but it is not the same Unicode character.
🤔
Did you know?
Empty set is Unicode U+2205 (decimal 8709) — glyph ∅ (EMPTY SET) in Mathematical Operators. HTML5 names it ∅ (aliases ∅, ∅). It denotes a set with no elements. Do not confuse it with Latin Ø (Ø) or a typed zero.
