Empty Relation
## Definition / Concept
The empty relation contains no ordered pair.
## Formula
$$R=\varnothing$$
## Conditions / Special Cases
For a non-empty set $A$, the empty relation is symmetric and transitive but not reflexive.
Therefore:
$$R=\varnothing\Rightarrow R\text{ is not an equivalence relation for }A\ne\varnothing$$
## Usage
- Used as a standard counterexample when checking reflexivity.