The relationship between the number of turns made by a driving gear to complete one full turn of the driven gear. If the driving gear turns four times to turn the driven gear once, the gear ratio would be 4 to 1. In most instances, the gear ratio is not even like 4:1 because the same teeth would be meshing with each other. Thus a ratio of 4.11:1, for instance, means that a particular tooth on one gear may eventually mesh with every one of the teeth on the other gear.
GEAR RATIO
Meaning of GEAR RATIO in English
English dictionary of automotive terms. Английский словарь автомобильных терминов. 2012