Splines are ridges or 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 matches the feminine spline on the gear. The splines on the pictured drive shaft match with the female splines in the heart of the clutch plate, while the smooth suggestion of the axle is definitely supported in the pilot bearing in the flywheel. An alternative solution to splines can be a keyway and crucial, gear rack though splines give a longer fatigue life.[2]