codewords

Codeword is a term used in signaling, cryptographic, and coding systems to denote a unit that stands for information encoded within a system. A codeword can represent a plaintext word or phrase, a status signal, or a data block, depending on the design. Codewords are chosen to be easy to recognize, distinguish, and transmit, while concealing or standardizing the intended meaning.

In cryptography and manual coding, codewords appear in codebooks that map between ordinary language and coded representations. A single codeword may stand for a common word, a concept, or a sentence, enabling messages to be sent with a reduced or less predictable symbol set. Security relies on the codebook remaining secret or on the codewords being unpredictable without the key.

In telecommunications and signaling, codewords or predefined signals are used to coordinate actions and indicate events. The NATO phonetic alphabet uses codewords such as Alpha, Bravo, Charlie to spell out messages clearly over voice links. Emergency services may use predefined codewords to signal situations quickly and unambiguously, such as "Code Red" or "Code Blue" in some organizations.

In coding theory and digital communications, a codeword is an element of a code, typically a fixed-length sequence over an alphabet. Codewords are designed so that, if a transmission is corrupted by noise, the original codeword can be recovered. Their length and minimum distance from other codewords determine error-detecting and error-correcting capabilities.

See also: codebook, cryptography, coding theory.