A worm gear is a mechanical system comprising a worm (a threaded shaft) and a worm wheel (a toothed gear) that transmits motion between shafts at a 90-degree angle. This setup is particularly effective for achieving high gear reduction ratios in a compact space. The worm 's threads engage with the worm wheel 's teeth, allowing the worm to drive the wheel but typically preventing the wheel from driving the worm due to self-locking.