In the sport of baseball, each of the nine players on a team is assigned a particular fielding position when it is their turn to play defense. Each position conventionally has an associated number, for use in scorekeeping by the official scorer: 1 (pitcher), 2 (catcher), 3, 4, 5, 6 (shortstop), 7, 8, and 9. Collectively, these positions are usually grouped into three groups: the outfield, the infield, and the battery. Traditionally, players within each group will often be more able to exchange positions easily ; however, the pitcher and catcher are highly specialized positions and rarely will play at other positions.