Compare the possible meanings
| Notation | Typical meaning | How to identify it |
|---|---|---|
∅ | Empty set | Set theory |
0 | Zero | Number |
{0} | Set containing zero | One-element set |
Ø | Slashed Latin letter O | Language or labels |
Examples
- |∅|=0 because the empty set has cardinality zero.
- ∅≠{0}; the second set contains one element.
- An equation may have solution set ∅.
How to decide
Ask whether the expression requires a set or a number. Use braces when zero is an element of a set.
How to verify the interpretation
Check the Unicode identity and the type required by the surrounding operation.