\unlhdThe symbol \unlhd is used to denote a relation known as 'triangle left' or 'normal subgroup' in group theory. It indicates that one group is a normal subgroup of another.
Indicates that H is a normal subgroup of G.
H \unlhd GShows that K is a normal subgroup of L.
K \unlhd LRepresents that N is a normal subgroup of M.
N \unlhd M