In group theory, given a group G under a binary operation *, we say that some subset H of G is a subgroup of G if H also forms a group under the operation *. More precisely, H is a subgroup of G if the restriction of * to H is a group operation on H. This is usually represented notationally by H ≤ G, read as "H is a subgroup of G". A proper subgroup of a group G is a subgroup H which is a proper subset of G (for example H ≠ G). The trivial subgroup of any group is the subgroup . They a… (More on Subgroup)