[{"Bold_text": "noun", "List Items": ["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 calledaddendum circle.an imaginary circle touching the tips of the teeth on a gear.", "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 calledaddendum circle.an imaginary circle touching the tips of the teeth on a gear."]}]