Splines are ridges or tooth[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 gear rack mounted on a shaft might use a man spline on the shaft that matches the feminine spline on the apparatus. The splines on the pictured drive shaft match with the female splines in the heart of the clutch plate, as the smooth suggestion of the axle is definitely supported in the pilot bearing in the flywheel. An alternative to splines can be a keyway and essential, though splines provide a longer fatigue life.[2]