Which term describes the physical structure of a robot, including gears and chains?

The term that best describes the physical structure of a robot, including gears and chains, is the mechanical structure. This encompasses all the physical components that make up the robot, allowing it to move and function as intended. The mechanical structure includes not just the gears and chains, but also the robot's frame, joints, and any other physical elements that contribute to its design and operation.

Understanding the mechanical structure is crucial for robot operation because it directly affects the robot's performance, stability, and capability to carry out tasks. The mechanical components must be precisely engineered to work together, ensuring that power and movement can be effectively transferred throughout the robot.