Splines are ridges or the teeth[1][2][3] on a drive shaft that mesh with grooves in a mating piece and transfer torque to this, maintaining the angular correspondence between them.

For instance, a equipment mounted on a shaft might use a male spline on the shaft that fits the feminine spline on the apparatus. The splines on the pictured drive shaft match with the female splines in the center of the clutch plate, as the smooth suggestion of the axle is definitely backed in the pilot bearing in the flywheel. An alternative to splines can be a keyway and planetary gearbox essential, though splines provide a longer fatigue life.[2]