Definition: The word "annex" in English refers to a document or set of documents that is added to an existing book, document, or other work for convenience or as part of a larger project. It's often used when it makes sense to add additional information to a document that isn't directly related, such as adding supplementary materials to support the main text. The term typically refers to a section of a book that is added later by the author in order to provide more depth and context not covered within the original text.