What is the call if a pitch is dropped during delivery and crosses a foul line?

When a pitch is dropped during delivery, the correct ruling is that it is considered a ball. This is based on the principle that the ball must be delivered to the batter in a specific manner. If a pitcher loses grip of the ball during their pitching motion, it is not deemed a strike or a foul ball, as those terms apply to situations where the ball is properly delivered. The ball crossing a foul line does not affect the ruling in this case, since the pitch was not completed due to the drop. An illegal pitch typically involves a violation of pitching rules, such as a violation of the pitching stance or motion, which is not applicable here. Thus, the call is a ball when the pitch is dropped during delivery.