How is "gear ratio" defined in the context of manual transmissions?

In the context of manual transmissions, gear ratio is defined as the ratio between the number of teeth on two gears. This is fundamental in understanding how power is transferred from the engine to the wheels. When two gears mesh, the number of teeth on the driving gear (the one connected to the engine) relative to the number of teeth on the driven gear (the one connected to the wheels) determines how torque and speed are altered.

A higher gear ratio means that the driving gear has fewer teeth compared to the driven gear, resulting in increased torque but a decrease in speed. Conversely, a lower gear ratio allows for higher speeds but less torque. This relationship is critical for optimizing vehicle performance under various driving conditions, making an understanding of gear ratios essential for anyone working with manual transmissions.