데이터 통신에서 수신측이 송신측에 전송된 데이터에 오류가 있거나 수락할 수 없음을 알리는 제어 문자.
A control character transmitted by a receiver to inform the sender that the data received contained errors or was not accepted.
예문:
"The protocol uses a NAK to signal that the data packet was corrupted during transit."
"Upon receiving a NAK, the transmitter immediately resends the last frame."