Worm gears can be classified into single-start and multi-start types based on the number of helical teeth on the worm. Additionally, they can be categorized as single-thread or double-thread based on the number of helical threads on the worm. Other classifications include non-throated and throated worm gears, which differ in the presence of a concave throat on the worm. These variations offer different gear reduction ratios, load capacities, and operational characteristics to suit various application needs.