forward gear ratio

reduction ratio / gear ratio

Voltage Standing Wave Ratio (VSWR) / voltage standing-wave ratio

jam to signal ratio (J/S ratio)

forward observer (FO), forward observation officer; (artillery) observer / spotter

forward gear

forward epicyclic gear trains

forward retracting landing gear

camshaft gear (timing gear)

gear reduction unit / gear-reduction unit

aspect ratio

fighter-to-administrative personnel ratio

high expansion-ratio

mass ratio

power-to-weight ratio

signal-to-noise ratio (SNR; S/N)

thrust-to-weight ratio

damping ratio

attenuation ratio

base pressure ratio

weight-horsepower ratio

weight-strength ratio

depression ratio

explosion ratio

infantry-armor ratio

fuel-air ratio

fuselage fineness ratio

compression ratio

engine pressure ratio (EPR)

excess air ratio

fuel hydrogen / carbon ratio

hub-tip ratio

mixture ratio