凸轮 (tū lún) is a mechanical engineering term referring to a rotating or sliding piece in a machine that transforms rotary motion into linear motion—or vice versa—by pushing against a follower. The character 凸 means 'convex' or 'protruding', describing its characteristic raised, asymmetrical shape; 轮 means 'wheel' or 'disc', indicating its circular form and rotational function. Together, they literally mean 'protruding wheel', capturing both its physical geometry and mechanical role.

This term appears primarily in technical contexts: automotive engineering (e.g., camshafts in engines), industrial machinery, robotics, and mechanical design. It is not used in everyday conversation but is essential vocabulary for students and professionals in mechanical fields. While visually reminiscent of a wheel, a cam differs fundamentally—it’s intentionally non-circular to produce specific motion profiles, unlike ordinary wheels designed for smooth rotation.