Screw

A cylinder or a cylindrical perforation having a continuous rib called the thread winding round it spirally at a constant inclination so as to leave a continuous spiral groove between one turn and the next used chiefly for producing when revolved motion or pressure in the direction of its axis by the sliding of the threads of the cylinder in the grooves between the threads of the perforation adapted to it the former being distinguished as the external or male screw or more usually the screw the latter as the internal or female screw or more usually the nut