In tennis, a serve that lands within the service box and is not touched by the receiver, resulting directly in a point for the server, constitutes an unreturnable serve. The ball must be legally served, adhering to all service regulations regarding foot placement and ball toss. For example, if a player serves the ball, it lands in the correct service box, and the opposing player makes no contact with the ball, the server is awarded a point due to the successful, unreturned service.
The occurrence of this type of service provides an immediate advantage to the server, allowing for a swift accumulation of points and potentially shifting the momentum of a match. Historically, a high frequency of these serves has been associated with dominant players, as it demonstrates precision, power, and strategic placement. Its effectiveness can greatly influence the outcome of a game or match.