What is the function of an index in a book?

An index serves a specific and practical purpose in a book by providing a systematic listing of important topics or terms, organized alphabetically along with their corresponding page numbers. This allows readers to easily locate specific information within the text without having to read through the entire book. The index acts as a navigational tool, enhancing the usability of the book, particularly for reference purposes.

Each entry in the index corresponds to key themes or subjects discussed in the text, making it easier for readers to find relevant sections quickly. This functionality supports scholarly research, study, or casual reading by helping readers focus on the content that is most pertinent to their needs.