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.
Skates generally come in three basic varieties: quad roller skates, inline skates or blades and tri-skates, though some have experimented with a single-wheeled quintessence skate or other variations on the basic skate design.ost roller derby leagues adopt the rules and guidelines set by the Women's Flat Track Derby Association or its male counterpart, Men's Roller Derby Association, but there are leagues that play on a banked track, as the sport was originally from c.1933-1998.