Subscriber station (10; 20; 30) for a serial bus system, having a communication control device (11; 21; 31) for creating a message (4; 5; 50; 500) which is to be transmitted serially to at least one further subscriber station (20; 30; 10) of the bus system, and/or reading a message (4; 5; 50; 500) which has been serially received from at least one further subscriber station (20; 30; 10) of the bus system, and a transmission/reception device (12; 22; 32) for transmitting the created message (4; 5; 50; 500) to at least one further subscriber station (20; 30; 10) of the bus system on a bus line and/or for receiving a message (4; 5; 50; 500) from the bus line, wherein the communication control device (11; 21; 31) and/or the transmission/reception device (12; 22; 32) are/is configured to provide in the message (4; 5; 50; 500) which is to be transmitted an ACK time window for an ACK signal and/or a NACK time window for a NACK signal for signalling whether at least one further subscriber station (20; 30; 10) has or has not detected an error in the transmitted message (4; 5; 50; 500), and wherein the transmission/reception device (12; 22; 32) is configured to apply no level to the bus line in the at least one provided time window (46, 47) during transmission to the at least one further subscriber station (20; 30; 10), and characterized in that the subscriber station (10; 20; 30) is configured to switch between two operating modes of a plurality of operating modes during operation of the bus system depending on the frequentness of a detected error, said operating modes comprising the following operating modes: an operating mode A) in which a signal which is identical for at least two of the subscriber stations (10; 20; 30) of the bus system is transmitted as the ACK signal and/or a signal which is identical for at least two of the subscriber stations (10; 20; 30) of the bus system is transmitted as the NACK signal, an operating mode B) in which the ACK signal and/or the NACK signal has a symbol which uniquely identifies the subscriber station (10; 20; 30) which has transmitted the signal (461; 471), and an operating mode C) in which the NACK signal is transmitted to the bus line only when the subscriber station (10; 20; 30) has exclusive, collision-free access to the bus line of the bus system in the NACK time window. a communication control device (11; 21; 31) for creating a message (4; 5; 50; 500) which is to be transmitted serially to at least one further subscriber station (20; 30; 10) of the bus system, and/or reading a message (4; 5; 50; 500) which has been serially received from at least one further subscriber station (20; 30; 10) of the bus system, and a transmission/reception device (12; 22; 32) for transmitting the created message (4; 5; 50; 500) to at least one further subscriber station (20; 30; 10) of the bus system on a bus line and/or for receiving a message (4; 5; 50; 500) from the bus line, wherein the communication control device (11; 21; 31) and/or the transmission/reception device (12; 22; 32) are/is configured to provide in the message (4; 5; 50; 500) which is to be transmitted an ACK time window for an ACK signal and/or a NACK time window for a NACK signal for signalling whether at least one further subscriber station (20; 30; 10) has or has not detected an error in the transmitted message (4; 5; 50; 500), and wherein the transmission/reception device (12; 22; 32) is configured to apply no level to the bus line in the at least one provided time window (46, 47) during transmission to the at least one further subscriber station (20; 30; 10), and characterized in that the subscriber station (10; 20; 30) is configured to switch between two operating modes of a plurality of operating modes during operation of the bus system depending on the frequentness of a detected error, said operating modes comprising the following operating modes: an operating mode A) in which a signal which is identical for at least two of the subscriber stations (10; 20; 30) of the bus system is transmitted as the ACK signal and/or a signal which is identical for at least two of the subscriber stations (10; 20; 30) of the bus system is transmitted as the NACK signal, an operating mode B) in which the ACK signal and/or the NACK signal has a symbol which uniquely identifies the subscriber station (10; 20; 30) which has transmitted the signal (461; 471), and an operating mode C) in which the NACK signal is transmitted to the bus line only when the subscriber station (10; 20; 30) has exclusive, collision-free access to the bus line of the bus system in the NACK time window.