Empty Set
Block: Mathematical Operators
- Symbol
- ∅
- Unicode
U+2205- Unicode name
- EMPTY SET
- Block
- Mathematical Operators
- Category
- Symbol, Math
- Type
- Unicode symbol
The empty-set symbol ∅ is U+2205. In mathematics it denotes the set containing no elements. It is a separate Unicode character from the Latin letter Ø, even though the two may look very similar in some typefaces.
What ∅ Means in Set Notation
The symbol ∅ denotes the empty set: a set with no elements. It is itself a set, so an expression can compare another set with ∅ or use it as part of a larger set-theoretic statement.
The visual idea of “nothing” should not be confused with the numeral zero or an empty text string. Those are different mathematical or computational objects. The empty-set symbol has a specific set-theoretic role.
Need to identify another character? Use what symbol is ∅? with the symbol itself, its Unicode value, or a description of how it looks.
Code-Point and UTF-8 Forms for ∅
The encoded identity can be represented without relying on the glyph. U+2205 = decimal 8709 = HTML ∅ / ∅. A Unicode escape-style representation is u2205. The UTF-8 byte sequence for the current glyph is E2 88 85.
These forms are useful when a font does not display the symbol clearly, when debugging copied text, or when comparing characters that look alike. Numeric references and escapes identify the underlying code point or sequence rather than a particular font drawing.
Empty Set, Zero, and Empty Values Are Different Ideas
The empty set is a mathematical set that has zero members; it is not the number 0. In programming and data formats, an empty string, null value, empty list, and empty set can also be different data values even when casual language calls all of them “empty.”
For symbol identification, U+2205 specifically identifies the empty-set sign. The surrounding notation determines how the set participates in the expression.
∅ Is Not the Latin Letter Ø
∅ EMPTY SET and Ø LATIN CAPITAL LETTER O WITH STROKE are encoded separately. The mathematical symbol is U+2205, while the letter is U+00D8. Some fonts draw them with different proportions or slash angles, but those visual cues are not guaranteed.
In formulas, replacing ∅ with Ø introduces a letter where a mathematical symbol was intended. In names or language text, replacing Ø with ∅ does the opposite. Checking the code point removes the ambiguity.