The ratio of output force to input force of a machine it its

Mechanical Advantage (MA)

Explanation:

The Mechanical Advantage (MA) of a machine is defined as:

where

is the output force

is the input force

Machines are used as force multiplier, which means that they are able to produce an output force which is greater than the input force (and example of machine is the lever). Therefore, the MA of a machine represents the "multiplication factor" of the input force: for instance, if a machine has a MA of 5, it means that the output force is 5 times the force applied in input.