"Law 21: No ball". A ball can be a no-ball for several reasons: if the bowler bowls from the wrong place; or if he straightens his elbow during the delivery; or if the bowling is dangerous; or if the ball bounces more than once or rolls along the ground before reaching the batsman; or if the fielders are standing in illegal places. A no-ball adds one run to the batting team's score, in addition to any other runs which are scored off it, and the batsman can't be dismissed off a no-ball except by being run out, hitting the ball twice, or obstructing the field.