The term 'addition to will' can be summarized by the word CODICIL, which is a seven-letter legal document that is used to make changes or additions to an existing will. A CODICIL is typically used when a person wants to make minor changes to their will without having to rewrite the entire document. It is important to note that a CODICIL must be signed and witnessed in the same way as a will in order for it to be legally binding.