A cam is a rotating or sliding mechanical component that converts rotary motion into linear or reciprocating motion. It typically works by pushing a follower, which moves in a straight line or back and forth as the cam rotates. The shape of the cam determines how the follower moves during each rotation, with common shapes including pear, circular, elliptical, square, or triangular. Cams are used in many machines such as car engines, printing machines, and household appliances to create controlled and timed movements.

In more detail, the cam is mounted on a rotating shaft, and as it spins, it pushes the follower through rise, fall, and dwell phases—where rise means the follower moves away from the cam center, fall means it returns, and dwell is a period of rest. For example, in an automobile engine, the camshaft uses cams to open and close engine valves at specific times.

There is also another context for CAM, which stands for computer-aided manufacturing, a software and technology system used to automate machine controls, but this is distinct from the mechanical cam mechanism.