There are several synonyms for the term "language reference book". A grammar guide is a book that covers the rules of a particular language's grammar. A thesaurus is a reference book that provides synonyms and antonyms for words. A dictionary is a book that provides definitions for words, often translated into several languages. An encyclopedia is a reference book that provides extensive knowledge about a particular subject or area, including language. A style guide is a reference book that provides rules and guidelines for writing, including punctuation, grammar, and formatting. A phrase book is a reference book that provides commonly used phrases and their translations, useful for international travelers. Ultimately, these reference books serve as valuable resources for those seeking to improve their linguistic skills.