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Syntax Definition cio 4338

Description: Extend class notation with Russell's definition description binder (inverted iota).

**Hypotheses**
Ref	Expression
wph	wff φ
vx	setvar x

**Assertion**
Ref	Expression
cio	class (℩xφ)

See definition df-iota 4340 for more information.

Colors of variables: wff setvar class