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.
A Daily Derby is a mock horse racing game. Players choose three horses, one each to finish first (win), second (place) and third (show); players also choose a race time from 1:40:00 to 1:49:99, by marking the last three digits of the time on the playslip.