The International Basketball Federation estimated that 450 million players participated in the game in 2007. One constant in the organized game regardless of location or teams is the referee. On-court officials ensure fair play based on the game's rules, using a standardized set of hand signals, combined with a blow of the whistle, to communicate fouls or violations. The most common signals used by collegiate and professional referees are the same, according to the NBA Official Referee Hand Signals and the "NCAA Basketball 2010 And 2011 Men's And Women's Rules."
The two most common offensive violations involve illegal motions with the basketball. Traveling, or moving both feet without dribbling the ball, is indicated by placing one forearm above and parallel to the other and the floor, then rotating your arms over one another a few times with your first clenched. The double dribble occurs when a player stops her dribble, then restarts it. The referee extends both arms straight out, moving one up and the other down, and alternating a few times.
Lesser violations include the three-second lane violation -- extend your middle, ring and pinky fingers while curling your thumb and index finger, hold your arm straight and sweep the arm out and back -- and the five-second inbound violation -- hold your arm out straight with an open hand signaling five.
In the rare instance of an offensive foul, called when the ballhandler makes contact with a defender who has established position, a special motion is used. Place your right open palm against the back of your head with your elbow bent and level with your ear, then extend your left arm straight and point at the offending player.
The most common piece of information conveyed by basketball officials is possession. This is signaled by extending your arm, palm facing inward, in the direction of the basket at which the team gaining possession is shooting. The other most common informational signal deals with calling off a made basket. Bend your elbows inward with fingers extended, so one arm is over the other, then swing your arms outward to your side. This may be preceded by pointing with your index finger at a side or end line, if the ballhandler goes out of bounds, or by calling a jump ball. Jump balls are indicated by extending your arms over your head, clenching your fist and extending your thumbs upward.
The only time a referee signals a made shot is on a three-pointer, doing so by raising both arms up straight and parallel to one another.
Calling a Defensive Foul
Fouls are typically committed by the person defending the person with the ball, who may be in the act of shooting. In the case of a foul on a shot, the referee with blow the whistle and wait to see if the ball goes in. If it does, hold your arm out bent at the elbow with your fist clenched, and quickly pump your forearm downward so the arm straightens. If not, simply call the foul. If the foul happened before the player began the shooting motion and the ball successfully enters the goal, the referee can call off the score as explained in the previous section.
Types of Defensive Fouls
The three main defensive fouls are the hold, push and block. Calling a holding foul involves bending your right arm at the elbow, fist clenched, in front of your body and grabbing your forearm with your left hand. Pushing fouls are called by extending your arms, palms opened, in front of you as if you were committing the push. A blocking foul is called by placing your hands on your hips, elbows extended.
Prior to signaling the type of foul committed by a defender, a referee can call the play dead and indicate who committed the foul using the bird dog signal. Extend your right arm in the air with your fist clenched, then extend your left arm, with fingers straight, pointing at the defender who committed the foul.
Basketball referees can call two fouls with more serious implications. A technical foul, indicated by the forming the letter T with your hands, is assessed when a player or coach exhibits conduct detrimental to the game. In the college game, an intentional foul is called when you believe a player was going after the ballhandler, not the ball itself. This is signaled clenching your fists, raising them above your head and crossing them over your head.