∅
Empty Set
- Unicode
- U+2205
- Category
- Math
- HTML Entity
- ∅
- CSS
- \2205
The empty set symbol (∅) is a mathematical notation used to represent a set that contains no elements. Introduced by the Bourbaki group in the mid-20th century, its design was inspired by the letter Ø in the Danish and Norwegian alphabets. Beyond formal set theory, it frequently appears in linguistics, computer science, and technical documentation to denote a null value, an empty string, or a lack of results.
How to Type
- Windows
- Type 2205 then Alt+X (in Word) or Win + . then search 'empty set'
- macOS
- Control + Command + Space then search 'empty set'
- Linux
- Ctrl + Shift + U then type 2205 and press Enter
- HTML
- ∅ or ∅
In Programming
While rarely used in literal source code due to syntax rules, the empty set symbol often appears in technical documentation to represent an empty array, null database result, or void state. Developers typically use native language constructs like `[]`, `{}`, or `null` instead of the Unicode character in actual code execution.
Tags
Bourbaki notation
LaTeX emptyset
LaTeX varnothing
U+2205
empty collection
empty set notation
mathematics
no elements
nothing
null set
null set symbol
null value symbol
programming empty set
set theory
void
Ø vs ∅