ADDENDUM
addendum, supplement, postscript
(noun) textual matter that is added onto a publication; usually at the end
Source: WordNet® 3.1
Etymology
Noun
addendum (plural addenda or addendums)
Something to be added; especially text added as an appendix or supplement to a document.
A postscript.
(engineering) The height by which the tooth of a gear projects beyond (outside for external, or inside for internal) the standard pitch circle or pitch line.
Source: Wiktionary
Ad*den"dum, n.; pl. Addenda. Etym: [L., fr. addere to add.]
Definition: A thing to be added; an appendix or addition. Addendum circle
(Mech.), the circle which may be described around a circular spur
wheel or gear wheel, touching the crests or tips of the teeth.
Rankine.
Source: Webster’s Unabridged Dictionary 1913 Edition