A type of base hit in which the batter safely reaches second base by hitting the ball fair and not being called out. If the batter reaches second base by way of a fielding error or a fielder's choice, then he or she won't be awarded a double. A double can also be scored if the ball successfully lands into the field of play and then bounces out of play-this is known as a "ground rule double".
In baseball statistics and stats lines, doubles will often be recorded under "2B".
Generally speaking, for a double to be achieved the hitter needs to bat the ball into the outfield, usually either down the line or between the gaps in the outfield so as to have enough time to reach second base.