In
mathematics, a
normal subgroup H of a
group G is a
subgroup invariant by conjugation; that is, for each element
h in
H and each
g in
G, the element
h-1 g h is still in
H.
Another way to put this is saying that right and left cosets of H in G coincide:
- H g = g g-1 H g = gH for all g in G.