Cam: A device for converting circular or rotary motion into reciprocating motion. It is a disc or collar with an irregularly shaped edge, which operates in contact with a rod or lever, and causes it to oscillate, or to move to and fro.

• 凸轮:把旋转动力转为往复力的机件。它是一个不规则形的圆碟或圆环，和一个杆或棒连接运作，使它上下或往来摆动。