Dedendum vs. Addendum — What's the Difference?

The difference between the radius of the pitch circle of a gear and its root circle

An addendum or appendix, 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 gerundive addendum, plural addenda, "that which is to be added," from addere (lit. ''give toward'', compare with memorandum, agenda, corrigenda).

An item of additional material added at the end of a book or other publication.

The radial distance from the pitch circle of a cogwheel or wormwheel to the crests of the teeth or ridges.

Something added or to be added, especially a supplement to a book.

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.

A thing to be added; an appendix or addition.

Textual matter that is added onto a publication; usually at the end