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.

noun

addition , adjunct , appendage , appendix , attachment , augmentation , codicil , extension , extra , postscript , rider , supplementnotes:an addition is something that , when added , serves simply to augment or extend that to which it has been added , leaving the character of the original unchanged; an addendum forms a separate distinguishable portion of the whole and it first meant \'a thing to be added\'