worm gear

One-way gearing system (only the screw can drive the wheel) for slowing down the speed of rotation between two perpendicular axles; it is used especially in the automobile industry (Torsen differential).

gear tooth

Protrusion on the gear wheel; the teeth of one wheel enter the gaps of another wheel to form a gearing system.

shaft

Cylindrical part that transfers the rotational movement of one part to another.