a pl. of addendum.

( used with a singular verb ) a list of things to be added

The addenda in the back of the book runs to thirty pages.

a thing to be added; an addition.

an appendix to a book.

Machinery .

the radial distance between the tip of a gear tooth and the pitch circle of a gear or the pitch line of a rack. Compare dedendum .

Also called addendum circle. an imaginary circle touching the tips of the teeth on a gear.