A subgroup of a group can also be defined as another abstract group along with an injective homomorphism (or embedding) from that abstract group to the given group. Here, the other abstract group can be naturally identified via its image under the homomorphism, which is the subgroup in a more literal sense.
For the skate brand of the same name, see Roller Derby (brand). Roller derby is a contact sport played by two teams of five members roller skating in the same direction around a track. Game play consists of a series of short match ups (jams) in which both teams designate a jammer who scores points by lapping members of the opposing team.
How Big is a Roller Derby Track? The roller derby track is almost oval shaped. Its inside line is a perfect oval, 25 feet (7.6m) across and 60 feet (18.3m) long. The track itself varies between 13 and 15 feet (4 -4.6m) wide so the outside line of the oval is an irregular shape.