End-of-book matter is a term used to refer to the material that appears at the end of a book, such as appendices, indices, and ADDENDA. ADDENDA is a plural form of the Latin word addendum, which means 'something to be added'. It is typically used to refer to supplementary material that is added to the end of a book or document. This material can include additional information, corrections, or other relevant material that was not included in the original text.