Definition df-id 3993

Description: Define the identity relation. Definition 9.15 of [Quine] p. 64. For example, 5 I 5 and ¬ 4 I 5. (Contributed by NM, 13-Aug-1995.)

Assertion

Ref	Expression
df-id	⊢ I = {⟨x, y⟩ ∣ x = y}

Distinct variable group:   x,y

Detailed syntax breakdown of Definition df-id

Step	Hyp	Ref	Expression
1		cid 3988	. 2 class I
2		vx	. . . 4 setvar x
3		vy	. . . 4 setvar y
4	2, 3	weq 1365	. . 3 wff x = y
5	4, 2, 3	copab 3780	. 2 class {⟨x, y⟩ ∣ x = y}
6	1, 5	wceq 1223	1 wff I = {⟨x, y⟩ ∣ x = y}

This definition is referenced by:  reli  4380  ideqg  4402  opabresid  4574  cnvi  4643  dffun2  4827  ider  6038