In volleyball, what does an ace refer to?

An ace in volleyball specifically refers to a serve that is not returnable, meaning the receiving team fails to touch the ball or is unable to make a legal play on the ball. This is an impressive achievement for the server, as it demonstrates not only their skill in serving but also the inability of the opposition to respond effectively. Aces can occur due to the speed, placement, or spin of the serve, making it difficult for the receiving team to anticipate and react.

The other options pertain to different aspects of the game. For example, a point scored by the opponent does not define an ace, and a successful block is a defensive play rather than a direct result of a serve. A ball that hits the net and goes over may result in a point but is not classified as an ace. Thus, the accurate definition of an ace is centered on the notion that it results from an effective serve that the receiving team cannot handle.