Indicates the widthwise boundaries of the court in a one-vs-one match. Singles Line: It is the equivalent of the doubles line, but for singles matches.During singles matches, it is irrelevant. During a doubles match, it indicates the boundary of the court widthwise. Doubles Line: As the name indicates, the doubles line is only relevant during doubles matches.It serves two purposes: 1) When a player is serving, he or she must stand behind the baseline and 2) If a player hits a shot that lands past the baseline, the shot is considered out and the player will lose the point.

Baseline: The baseline indicates the boundary of the court lengthwise.The picture above contains the name of every line on a tennis court.