Tennis gives the server the right to keep play moving, but that right has a fairness limit. The receiver must play to the reasonable pace of the server, while the server must not serve until the receiver is ready. Most disputes come from confusing "reasonable pace" with permission to quick-serve, or from treating every receiver delay as an automatic let.
The service rule balances two duties. The server must wait until the receiver is ready to receive, and the receiver must be ready within a reasonable time at the server's pace. The receiver does not get unlimited time to towel off, reset, or slow the match, but the server also cannot create an unfair point by serving while the receiver is clearly not prepared.
A receiver is expected to keep up with the server's reasonable rhythm. That matters because tennis is built around continuous play, not a receiver-controlled reset before every point. A player who repeatedly turns away, walks to the towel, adjusts equipment, or signals late after the server is ready may be delaying play.
A server may serve promptly after the score is called and the point is ready to begin, but not as a trick while the receiver is still recovering position, looking away, retrieving a ball, or otherwise plainly unready. The practical question is not whether the serve was fast. It is whether the receiver had reached a ready receiving position before the ball was served.
If the receiver swings at or otherwise attempts to return the serve, officials generally treat the receiver as having been ready. A receiver cannot normally take a chance on returning the ball and then claim unreadiness only after the return misses. If the receiver was genuinely not ready, the cleaner response is to make no play and raise the issue immediately.
When a serve is delivered before the receiver is ready and the receiver makes no attempt to play it, the point is not decided by that serve. The usual treatment is a let for that service attempt, not a fault against the server and not a point for the receiver. If the same problem keeps happening, the official may warn or penalize the player causing the delay rather than endlessly replaying serves.
The standard continuous-play framework allows 25 seconds between points, with longer limits at changeovers and set breaks unless the competition uses an approved variation. That clock does not give the receiver a separate right to be last-ready every point. It also does not let the server ignore a receiver who is reasonably delayed by a ball on court, an official correction, or another problem outside the receiver's control.
A raised hand is a useful signal, but it is not a veto over the server's pace. If the receiver signals because of a real reason, such as a ball behind the court or not yet being set after the previous point, the server should wait. If the receiver keeps using the signal after the server is reasonably ready, the official can treat that as delay.
The score call and shot clock help organize the restart, but readiness is still judged from the players' actual situation. A serve after the score is called can still be improper if the receiver was obviously unready for a legitimate reason. At the same time, a receiver who is ready and then looks away late cannot use that alone to erase a serve.
Chair umpires and roving officials look for fairness and pattern. A single rushed serve with an unready receiver is usually handled by replaying the serve. Repeated receiver delay can lead to time or code penalties under the event rules. Repeated server attempts to catch the receiver unready can be stopped by the official and may also become a conduct issue if it is used to disrupt the opponent.