What is a data dictionary in the context of databases?

A data dictionary serves as a centralized source of metadata in the context of databases, providing essential descriptive information about the data contained within a database. This metadata includes details such as data types, constraints, relationships, and meanings of various data elements. For example, it might specify that a certain field represents a date, can accept null values, or has a specific range of acceptable values. By consolidating this information, a data dictionary helps users understand the structure, organization, and semantics of the data, which is vital for effective database management, data integrity, and collaboration among users.

This centralization of metadata facilitates communication and consistency among developers, analysts, and users, ensuring everyone interprets the data in the same way. It can also aid in data governance and compliance by providing clear documentation on data usage and definitions.