A minor point - the entry describes an addendum as something that is "to be added" which is may well be correct as a Latin future participle (not my area). However, in common English usage, it may also describe that which has already been added as in "You'll find it in the addendum/addenda to the document." I would hesitate to use the mangled macaronic "addendums" as the plural. —This unsigned comment was added by 18.104.22.168 (talk).
Is there an adjectival form of this term? We have the verb addend, I see, but is there even an adjectival form of this term, and if so, what would it be—addendary perhaps, or perhaps something more consistent with the Latin? allixpeeke (talk) 07:29, 19 May 2017 (UTC)