What term describes the amount by which the dedendum in a gear exceeds the addendum of its mating pinion?

The correct term for the amount by which the dedendum of a gear exceeds the addendum of its mating pinion is "clearance." In gear design, clearance refers to the vertical distance between the top of the pinion teeth (addendum) and the bottom of the gear teeth (dedendum). This gap ensures that the gear can mesh properly without interference during operation and allows for slight misalignments.

This concept is important for maintaining smooth operation, reducing noise, and preventing wear or damage to the gear teeth. Adequate clearance is necessary for the operational efficiency of gear systems, ensuring that they can handle variations in load and environmental conditions.

The other options refer to different aspects of gear design. For example, tip relief is a modification made to the tips of gear teeth to help reduce stress and improve meshing during the initial contact phase, while top land refers to the flat surface at the top of the gear teeth. "Space" doesn't specifically refer to the relationship between the dedendum and addendum. Thus, "clearance" is the most accurate term in this context.