| Metamath Proof Explorer |
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Related theorems GIF version |
| Description: Extend wff definition to include the membership connective between classes. |
| Ref | Expression |
|---|---|
| cA | class A |
| cB | class B |
| Ref | Expression |
|---|---|
| wcel | wff A ∈ B |
| Colors of variables: wff set class |