Badminton/Scoring system and service

The basics
Each game is played to 21 points, with players scoring a point whenever they win a rally (this differs from the old system, where players could only win a point on their serve). A match is the best of three games. At the start of the rally, the server and receiver stand in diagonally opposite service courts (see court dimensions). The server hits the shuttlecock so that it would land in the receiver's service court. This is similar to tennis, except that a badminton serve must be hit below waist height and with the racquet shaft pointing downwards, the shuttlecock is not allowed to bounce and in badminton, the players stand inside their service courts unlike tennis. When the serving side loses a rally, the serve passes to their opponent(s) (unlike the old system, there is no "second serve" in doubles). In singles, the server stands in his right service court when his score is even, and in his left service court when his score is odd. In doubles, if the serving side wins a rally, the same player continues to serve, but he changes service courts so that he serves to each opponent in turn. If the opponents win the rally and their new score is even, the player in the right service court serves; if odd, the player in the left service court serves. The players' service courts are determined by their positions at the start of the previous rally, not by where they were standing at the end of the rally. A consequence of this system is that, each time a side regains the service, the server will be the player who did not serve last time.

Details
When the server serves, the shuttlecock must pass over the short service line on the opponents' court or it will count as a fault. If the score reaches 20-all, then the game continues until one side gains a two point lead (such as 24-22), up to a maximum of 30 points (30-29 is a winning score). At the start of a match, a coin is tossed. The winners of the coin toss may choose whether to serve or receive first, or they may choose which end of the court they wish to occupy. Their opponents make the remaining choice. In less formal settings, the coin toss is often replaced by hitting a shuttlecock into the air: whichever side the corked end points will be the side that serves first. In subsequent games, the winners of the previous game serve first. These can also be called rubbers. If one team wins a game they play once more and if they win again they win that match, but if they lose they play one more match to find the winning team. For the first rally of any doubles game, the serving pair may decide who serves and the receiving pair may decide who receives. The players change ends at the start of the second game; if the match reaches a third game, they change ends both at the start of the game and when the leading pair's score reaches 11 points. The server and receiver must remain within their service courts, without touching the boundary lines, until the server strikes the shuttlecock. The other two players may stand wherever they wish, so long as they do not insight the opposing server or receiver.

Faults
Players win a rally by striking the shuttlecock over the net and onto the floor within the boundaries of their opponents' court ( Singles: the side tramlines are out, but the back tramline is in. Doubles: the side tramlines are in, but the back tramline is out (service only)). Players also win a rally if their opponents commit a fault. The most common fault in badminton is when the players fail to return the shuttlecock so that it passes over the net and lands inside their opponents' court, but there are also other ways that players may be faulted. Several faults pertain specifically to service. A serving player shall be faulted if the shuttlecock is above his waist (defined as his lowest rib) at point of contact, or if his racket's head is not pointing downwards at the moment of impact. This particular law was modified in 2006: previously, the server's racket had to be pointing downwards to the extent that the racket head was below the hand holding the racket; and now, any angle below the horizontal is acceptable. Neither the server nor the receiver may lift a foot until the server has struck the shuttlecock. The server must also initially hit the base (cork) of the shuttlecock, although he may afterwards also hit the feathers as part of the same stroke. This law was introduced to ban an extremely effective service style known as the S-serve or Sidek serve, which allowed the server to make the shuttlecock spin chaotically in flight. Each side may only strike the shuttlecock once before it passes back over the net; but during a single stroke movement, a player can contact a shuttlecock twice (this happens in some sliced shots). A player may not, however, hit the shuttlecock once and then hit it with a new movement, nor may he carry and sling the shuttlecock on his racket. It is a fault if the shuttlecock hits the ceiling.

Lets
If a let is called, the rally is stopped and replayed with no change to the score. Lets may occur due to some unexpected disturbance such as a shuttlecock landing on court (having been hit there by players on an adjacent court) or in small halls the shuttle may touch an overhead rail which can be classed as a let. If the receiver is not ready when the service is delivered, a let shall be called; yet, if the receiver attempts to return the shuttlecock, he shall be judged to have been ready. There is no let if the shuttlecock hits the tape (even on service).