A look at the rules and scoring for some Olympic sports:

TABLE TENNIS

Table tennis medals are awarded in men's and women's singles, and the men's and women's team event. Each country enters a maximum of two players in singles, and three in team.

Olympic table tennis is a knockout tournament. Singles matches are the best-of-seven games. Team matches are the best of five. A team event consists of two singles matches, followed by a doubles matches. Two more singles matches are played if needed.

A game ends when one player reaches 11 points. The serve alternates every two points. The minimum advantage for a completed set is two points.

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TAEKWONDO

The London Games are the first Olympics to use electronic scoring for taekwondo. Competitors will wear an electronic body protector and protective equipment for their feet, shins, hands, forearms and head.

Kicks and punches to the body score one point apiece and are automatically registered if they strike their opponent's body protector with enough force. Punches to the head are not allowed and all kicks must be above the belt.

Kicks to the head score three points and are registered manually by four corner judges or the referee. Fighters score an extra point for any kick with a spinning technique.

In the case of a disputed call, an athlete's coach may request a video replay. If they are wrong, they lose the right to further appeals.

Each taekwondo match includes three two-minute rounds. If the score is tied at the end, it goes into a one-minute "sudden death" round that ends as soon as a fighter scores a point.

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TRIATHLON

The individual endurance competition features athletes competing nonstop in three different sports in sequence. In its most common form, a triathlon involves swimming, cycling and running. Races vary in distance — at the Olympics, it's the intermediate version with a 1.5-kilometer swim, 43k ride and 10k run.

The time an athlete spends in the transition zones while changing their gear for the next discipline is counted in their race time. The jury can award time penalties for violations such as hindering other competitors or for an incomplete transition like still wearing your race helmet during the run. The winner is the first athlete to complete all three disciplines.

Men's and women's races often take place simultaneously, but they are separated at the Olympics, with the women competing on Aug. 4, followed by the men three days later.

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VOLLEYBALL

The indoor sport features two teams of six players apiece on a court separated by a net. A player on one team serves from the backcourt to the other side of the net, and the opposing team tries to return the ball. Play continues until one of the teams win a point. Points are won when a team grounds the ball on the opposite court, or one of the teams commits a fault.

Teams on each side of the net can only touch the ball three times in trying to return it to the other side. A single player cannot touch the ball consecutively. Other faults include hitting the ball out of bounds and hitting the ball while it is over the net but still on the opponent's side.

A set is won by the first team to reach 25 points, with a minimum advantage of two points. A match is won by the first team to win three sets. If there is a 2-all tie, the deciding set is played to 15 points, with a minimum advantage of two points.

Volleyball was originally played as a round-robin tournament, but the qualifying countries are now separated into pools, with the top four finishers from each going on to compete for spots in the quarterfinals, semifinals and the final.

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WATER POLO

Each team in the pool has six field players and one goalkeeper. The game consists of four eight-minute periods. A team wins by scoring more goals than the opposing side.

A team cannot have possession of the ball for more than 30 seconds. After 30 seconds, possession passes to the other team.

There are two types of fouls — ordinary and major.

A player who commits a major foul, such as holding, intentionally splashing an opponent in the face or interfering with a free throw, is excluded from the game for 20 seconds, giving the opposing team what is called a "man up" situation, similar to a power play in ice hockey.

If a defender commits a major foul inside the five-meter line, then the attacking team is awarded a penalty shot on goal from five meters.

Any player who commits three major fouls in a match is sent off for the rest of the game.

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WEIGHTLIFTING

Lift more weights than the others and you win. It sounds straightforward but there is more strategy involved in weightlifting than you might think. Competitors get only six lifts so they must use them wisely, making sure they don't waste attempts on weights that are either too light or too heavy.

There are two types of lift, which must be approved by at least two of the three judges.

In the snatch, athletes lift the bar from the floor in one continuous motion, rising out of a squat to hold the bar overhead with extended arms.

The clean and jerk is performed in two stages. First the lifter pulls the bar to shoulder height while in a squat. Then he or she rises and pushes the bar overhead to finish in an upright position.

Competitors get three attempts at the snatch and three attempts at the clean and jerk. The total score combines their best lift in each.

If two lifters are tied when the weights are added up, the lifter with the lower body weight wins. If the lifters have the same weight, whoever performed the biggest lift first is declared the winner.

Competitors are divided into weight categories, eight for men and seven for women.

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WRESTLING

Wrestling competitors are divided into weight classes: 14 for men and four for women.

There are two styles of Olympic wrestling: freestyle and Greco-Roman. The major difference between the two disciplines is that holds below the waist are forbidden in Greco-Roman.

Each match consists of three two-minute periods. The wrestler who scores the most technical points wins the period unless one competitor pins the other, which automatically ends the match. Otherwise, the competitor who wins the most periods wins the match.

To score a pin, which is also known as a fall, a wrestler must hold his or her rival's shoulder blades to the mat for at least half a second. Wrestlers also can stop a period by scoring six or more points than their opponent. That's known as technical superiority.

Each weight class begins and ends in the same day, after previously being contested for two or more days.