Pronunciation: (u-den'dum), [key]
—pl. -daPronunciation: (-du) [key] for 1, 2; -dums for 3.
1. a thing to be added; an addition.
2. an appendix to a book.
a. the radial distance between the tip of a gear tooth and the pitch circle of a gear or the pitch line of a rack. Cf. dedendum.
b. Also called adden'dum cir'cle. an imaginary circle touching the tips of the teeth on a gear.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.