A balk is an illegal move made by or related to the pitcher. Balks result in a dead ball and all base runners (not including the batter) advancing one base. Balks are only called when there are one or more runners on base, otherwise, an illegal move by the pitcher would only result in a ball.
Common circumstances in baseball that constitute a balk are the following:
|The catcher steps on home plate or moves in front of it without the ball when a runner on third base is stealing home.||The pitcher is charged with a balk.|
|If the catcher is not in the catcher's box by the time the ball leaves the pitcher's hand.||The pitcher receives a balk.|
|The pitcher fails to complete the pitching motion with set or windup while simultaneously a base runner interrupted the pitcher's delivery.||No balk is given, instead it is a "scratch" or do-over.|
|The pitcher does not complete his pitching motion because the batter steps out of the batter's box.||No balk is called. It is a batter's box violation.|
|The pitcher disengages the rubber by stepping off with his free foot.||Balk! The pitcher must step off the plate with his pivot foot.|
Baseball has lots of rules for pitchers. If a pitcher breaks one of these rules he will be called for a balk. Commonly, balks are called when the pitcher pretends to pitch, but does not actually follow through with the pitch. The reason a pitcher might do this is to deceive the base runners; he would pretend to pitch, then attempt to pick off a base runner instead of delivering the pitch, thus catching the runner off-guard. Since this is an illegal method of deception, the rule of balks is implemented.