codebook

A codebook is a set of codes and their meanings used for encoding information or describing a dataset. The term is used in several disciplines, with different specialized meanings depending on the context.

In data management and statistics, a codebook (or data codebook, data dictionary) documents the variables in a dataset. It typically lists variable names, labels, data types, allowed values or categories, coding schemes for categorical variables, units of measure, missing value conventions, and any derived or computed fields. The codebook serves as a reference for data collection, cleaning, analysis, and replication, helping users interpret values and ensure consistency across studies.

In cryptography, a codebook is a collection of code words and their plaintext equivalents, used to convert messages into coded form. Codebooks were common in historical substitution systems and can be used with code phrases or nomenclatures. Modern cryptography relies on algorithmic cryptographic primitives rather than static codebooks; if a codebook is compromised, the encoded messages become vulnerable.

In signal processing and data compression, a codebook is a set of representative vectors or patterns used to encode data efficiently. During encoding, each input segment is matched to a codeword from the codebook, and the index is transmitted or stored. Codebooks are central to vector quantization, including algorithms such as the Linde–Buzo–Gray method and k-means clustering, and are used in image, audio, and multimedia compression.