It is called addendum to the Appendix or to the series of annotations that will be added in a written work once it is finished and that will have the mission of making clarifications, completing it, or failing that, rectifying any question that is exposed in it..
It should be noted that this concept is used almost exclusively in written works, such as books, contractual documents, technical manuals, instructions, legal texts, medical treatises, among others. As with the appendix, the addendum usually appears arranged at the end of a book or any of the writings mentioned above.
In the case of books, the addendum usually has the mission of accompanying the central work and especially explaining the inconsistencies that emerged from it after its edition and that as it was already finished it is necessary to express them outside the main body and by This is because they are added to the end of the text. This usually happens with those works that have already been printed and in which it would be really expensive to reprint them, then, the addendum resource is the best to reduce the cost and allow the reference of errors.
For their part, legal contracts also usually have addenda when it is necessary to change, expand or define some of the conditions set forth in them. Normally, the addendum will allow adding specific details or conditions that were not established in the original for any reason but that are fundamental in a contractual relationship to avoid future problems.
In manuals or instructions, the addendum is a very common resource since it allows adding a certain information or specific question that arises once it is published.
