Definition df-subg 19101

Description: Define a subgroup of a group as a set of elements that is a group in its own right. Equivalently (issubg2 19119), a subgroup is a subset of the group that is closed for the group internal operation (see subgcl 19114), contains the neutral element of the group (see subg0 19110) and contains the inverses for all of its elements (see subginvcl 19113). (Contributed by Mario Carneiro, 2-Dec-2014.)

Assertion

Ref	Expression
df-subg	⊢ SubGrp = (𝑤 ∈ Grp ↦ {𝑠 ∈ 𝒫 (Base‘𝑤) ∣ (𝑤 ↾s 𝑠) ∈ Grp})

Distinct variable group:   𝑤,𝑠

Detailed syntax breakdown of Definition df-subg

Step	Hyp	Ref	Expression
1		csubg 19098	. 2 class SubGrp
2		vw	. . 3 setvar 𝑤
3		cgrp 18911	. . 3 class Grp
4	2	cv 1541	. . . . . 6 class 𝑤
5		vs	. . . . . . 7 setvar 𝑠
6	5	cv 1541	. . . . . 6 class 𝑠
7		cress 17202	. . . . . 6 class ↾s
8	4, 6, 7	co 7369	. . . . 5 class (𝑤 ↾s 𝑠)
9	8, 3	wcel 2114	. . . 4 wff (𝑤 ↾s 𝑠) ∈ Grp
10		cbs 17181	. . . . . 6 class Base
11	4, 10	cfv 6500	. . . . 5 class (Base‘𝑤)
12	11	cpw 4542	. . . 4 class 𝒫 (Base‘𝑤)
13	9, 5, 12	crab 3390	. . 3 class {𝑠 ∈ 𝒫 (Base‘𝑤) ∣ (𝑤 ↾s 𝑠) ∈ Grp}
14	2, 3, 13	cmpt 5167	. 2 class (𝑤 ∈ Grp ↦ {𝑠 ∈ 𝒫 (Base‘𝑤) ∣ (𝑤 ↾s 𝑠) ∈ Grp})
15	1, 14	wceq 1542	1 wff SubGrp = (𝑤 ∈ Grp ↦ {𝑠 ∈ 𝒫 (Base‘𝑤) ∣ (𝑤 ↾s 𝑠) ∈ Grp})

This definition is referenced by:  issubg  19104