Basically, gear is a toothed wheel designed to transmit motion or to change speed or direction to another toothed components or gear. Gear and its teeth are designed in a manner to minimize wear, vibration and noise, and to maximize the efficiency of transmission.

Due to difficulty in designing high power machineries mechanical engineers sometimes rely on electronic control and toothed belts. Whatever may be the case, gears are the optimal medium for high accuracy and low energy loss, even for high power machinery.

According to the meshing of toothed components gears are categorized into several types like, circular spur gears, rack and pinion spur gears, and worm gears. Helical and herringbone gears utilize curved teeth for efficient, high-capacity power transmission. Worm gears, driven by worms transmit motion between non-intersecting right-angle axes.