Call: Verbal utterance by a line judge or chair umpire declaring that a ball landed outside the valid area of play.
Cannonball: Somewhat archaic term for a very fast, flat serve.
Can opener: Serve hit by a right-handed player with slice, landing on or near the intersection of the singles tramline and service line in the deuce court.
Carve: To hit a groundstroke shot with a combination of sidespin and underspin.
Centre mark: Small mark located at the centre of the baseline. When serving the player must stand on the correct side of the mark corresponding with the score.
Challenge: When a player requests an official review of the spot where the ball landed, using electronic ball tracking technology.
Change-over (or change of ends): 90 second rest time after every odd-numbered game when the players change ends.
Chip: Blocking a shot with underspin, creating a low trajectory.
Chip and charge: Type of approach shot which involves hitting a slice shot while rapidly moving forward and following the shot into the net. Aimed at putting the opponent under pressure.
Chop: Shot hit with extreme underspin, opposite of topspin.
Closed stance: Classic technique in which the ball is hit while the hitter's body is facing at an angle between parallel to the baseline and with his back turned to the opponent.
Consolidate (a break): To hold serve in the game immediately following a break of serve.
Counterpuncher: Defensive baseliner.
Court: Area designated for playing a game of tennis.
Crosscourt shot: Hitting the ball diagonally into the opponent's court.
Cross-over: Player crossing the net into the opponent's court. It can be done either in a friendly fashion, or maliciously, thereby invoking a code violation. The latter sometimes happens when it is uncertain whether the ball on a decisive point landed inside or outside the court when playing on clay, thus leaving a mark.