The Rules of Tennis
The rules of tennis are officially determined by the International Tennis Federation (ITF). There are 30 in total and have all been summarised below. A complete and detailed version can be explored via a large downloadable PDF from the ITF website here.
The Court. A rectangle of a constant length. The width is slightly wider for doubles matches than it is for singles (The two areas are obviously marked on the court when you look at it). The court has a net stretched across the middle of it, this also varies based on singles or doubles matches. The short sides of the rectangle are referred to as the baselines and the long sides are the sidelines. Each half of the court is divided again by the service line.
Permanent Fixtures. Are located around the court such as the umpire's chair, seating for the crowd, back and side stops etc.
The Ball. Must be red, orange or green. A ball can be exchanged either after an odd number of games or at the beginning of a set.
The Racket. One set of strings in a crossed pattern. A Player may not use more than one at a time.
Set. A set is six games. To win a set you need to win by two clear games. The set is continued until the required margin is achieved.
Match. A match is three or five sets. First one to win two or three sets (number agreed before hand) wins the match.
Scoring. Scoring proceeds in order: love (meaning nil or 0), 15, 30, 40 and then game. Deuce is called when two players have both won 40 points. After deuce a point scored takes a player to advantage, if that player wins one more point then they win the game. If they don't then they go back to deuce again. A player must therefore win two points in a row after deuce in order to win the game. There are special rules around a tie break game. A player/team must score at least 7 points and be 2 points clear of their opponent in order to win. The game continues as long as necessary until the two points clear is achieved. Win a point when you hit the ball to the correct side of the court and then it hits a permanent fixture. Lose a point if you hit a permanent fixture first. In general, you lose the point for two consecutive faults, the player doesn't return the ball before it bounces twice, a player returns the ball and it lands outsides the court or hits a permanent fixture or you hit the ball before it passes the net.
Service. Starts from behind the baseline and lands between the imaginary extension of the center mark and the sideline. Release with the hand and then hit with the racket. Service starts from alternate sides of the court starting from the right side at the start of every game. Serve across the net into the service court diagonally opposite. The receiver can stand outside the lines of the court. In a singles game, service changes after every game. In doubles the pair chooses who serves for their first game and then it rotates between them every other game when it's their turn to serve again. The decision on who receives the ball works the same way. The ball is said to be in play as soon as it is served and it remains that way until either a point is scored or a fault or a let is called. Server can't serve until the receiver is ready, the receiver must play to the pace of the game however. Also need to let the ball bounce once when receiving the service.
Serving or Receiving. The choice of ends and the choice to be server or receiver in the first game is determined by toss before the first game. If a player wins the toss then they can require their opponent to make the choice. Players change ends on the first, third, fifth and then every odd game in a set. They change ends at the end of a set unless the set ends on an even game, in which case they change ends at the end of the first game in the next set.
Faults. A foot fault is called if the server steps outside of the service area. In general no foot movement is permitted except for slight movement. You are allowed one or both feet of the ground however. A Service fault is called when any of the service rules above are broken or the server misses the ball, hits a permanent fixture before the ground or hits the server or the server's partner. The server gets a second serve from the same side of the court if a fault occurs. A ball that touches a line is still on the court and in play.
Let. If the ball touches the net or the receiver and is otherwise good (lands in the correct service court) or is served when the receiver is not ready then it's a let and is served again. A let does not cancel a previous fault. A let means the point is replayed.