Let (Serve Rule)

If a serve touches the top of the net on its way over but still lands within the correct service box, it is a let, and the server simply replays that serve without losing the attempt — a let serve does not count as a first or second serve. If a serve clips the net and lands outside the correct box (long, wide, or in the wrong box), it is simply a fault, not a let, because the let rule only applies when the serve would otherwise have been good. Lets can occur on either a first or second serve, and there is no limit to how many times a let can be replayed in a row.

Beyond the net-cord serve let, "let" is also called more broadly any time a point needs to be stopped and replayed for reasons unrelated to either player's fault — a ball rolling onto the court from an adjacent court, a sudden distraction, or an umpire's judgment call that a player was unsighted are all typically handled as a let and the point replayed. In recreational and most amateur play without electronic net-cord sensors, players self-officiate by ear and sight, calling a let themselves the moment they hear or see the net cord affect the serve.