Definition 2.6.5.  Let G be a group, a, b ∈ G. We define:
a • b:= ab if G = [G, , e, i] (G is a set, :G × G → G is an operation on G, e ∈ G, i:G → G is a function such that (G, , e, i) forms a group)
Remarks.

This definition lets us multiply elements without decomposing the group.