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.
Blue-bellied Roller. The Blue-bellied Roller is a large bird, nearly the size of a Jackdaw at 28-30 cm. It has a dark green back, white head, neck and breast, with the rest of the plumage mainly blue. Adults have 6cm tail streamers. Sexes are similar, but the juvenile is a drabber version of the adult.