An addendum, in general, is an addition required to be made to a document by its author subsequent to its printing or publication. It comes from the Latin verbal phrase addendum est, being the gerundive form of the verb addo, addere, addidi, additum, "to give to, add to", meaning "(that which) must be added". Addenda is from the plural form addenda sunt, "(those things) which must be added". (See also Memorandum, Agenda, Corrigenda).