Subgroup
subset of a mathematical group that forms a group itself
In group theory, a branch of mathematics, given a group under a binary operation, a subset of is called a subgroup of if the elements also forms a group under the binary operation.
The situation could arise in which the subset does not comply with the binary operation. In that case, H would not be a subgroup.
For example, the even numbers are a subgroup of the integers, with addition as the binary operation.
