| Scoring system | The scoring system for modern tennis is based on that of its medieval ancestor, court tennis. In court tennis, a game comprised four rounds of 15 points each. That system was imposed on lawn tennis, as it used to be known, with the points numbered 15, 30, 45, and 60 (or game). Somewhere along the line, 45 was abbreviated to 40. The point is the basic building block; a game is made up of points, a set is made up of games, and a match is made up of sets. |
| Second flight | The flight of the ball after it bounces. |
| Seed | Before a tournament, certain players are ranked, based on their ability and recent performances. The process is called seeding, the rankings are called seeds, and the top-ranked player is called the top seed. Matches are then arranged so that the top-seeded players will not meet until the later rounds of the tournament. |
| Serve | The shot that begin each point. Standing behind the baseline, the player must toss the ball into the air and hit it into the diagonally opposite service court. The server is given two chances to make a valid serve. A failure is called a fault and a double fault results in loss of the point. On the first point, the server must be to the right of the center line, and then alternates sides with each point. In singles, the players alternate service throughout a match. In doubles, service alternates between the sides, and all four players serve in turn. |
| Serve and volley | A style of play in which the server takes the net after each successful serve in order to volley the opponent's return. |
| Server | The player whose turn it is to serve. |
| Service | See serve. |
| Service court | One of the two rectangles on each side of the net bounded by the service sideline, the service line, the center service line between them, and the net itself. Each service court is 21 feet deep and 13½ feet wide. |
| Service line | The line that marks the back boundary of the service courts on each side of the net. |
| Service line judge | An official who is responsible for determining whether a serve hits the court beyond the service line. The service line judges are stationed on the same side of the court as the umpire and on a line with the service lines. |
| Service sideline | That part of the singles sideline, between the net and the service line, that marks the outside boundary of the service court. |
| Service winner | A serve that the receiver hits without making a legal return. |
| Set | A set is a group of games that is won by the player or side that first wins at least six games with a two-game margin, unless a tie-breaker is employed. In major tournaments, there are usually five sets in a men's match and three in a women's match. See scoring system; tie-breaker. |
| Set point | A point that, if won by the leader, will result in winning the set. See also game point; match point. |
| Shot | The act of hitting the ball with the racket. |
| Sideline | The line that marks the side boundary of the court. The sidelines are 27 feet apart for singles and 36 feet apart for doubles. |
| Sideline judge | An official who is responsible for determining whether a shot lands outside the sideline or in the court. There are four sideline judges, two at each end of the court. |
| Sidespin | Spin around the ball's vertical axis, applied by drawing the racket strings horizontally across the ball at the moment of contact. |
| Singles | A match between two players. |
| Singles court | The court used for a singles match, which is 27 feet wide. |
| Singles sideline | One of the two lines that mark the side boundaries of the singles court. |
| Slice | A shot hit with both backspin and sidespin; as a verb, to hit such a shot. |
| Smash | An overhead shot that is hit very hard and down into the opponent's side of the net. |
| Snap volley | A volley given extra velocity by wrist action at impact. |
| Stop volley | A volley, hit with little motion of the racket, that drops just over the net. |
| Straight sets | Descriptive of a match in which one player wins all the sets. |
| Strings | The hitting surface of the racket, made up of interlaced strings of gut or synthetic material. |
| Stroke | A swing at the ball; a shot. |
| Sudden death | A tie-breaker of predetermined length. The most commonly used are the 9-point tie-breaker, in which the first player to score 5 points is the winner, and the 13-point tie-breaker, which is won by the first player to score 7 points. |
| Sweet spot | The optimum hitting area, around the middle of the racket face. |