ad·den·dum /əˈdɛndəm/
  附錄,附加物
  Ad·den·dum n.; pl. Addenda   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.
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  addendum
       n : textual matter that is added onto a publication; usually at
           the end [syn: supplement, postscript]
       [also: addenda (pl)]