coefficient

noun

1. a factor that contributes to produce a result
2. Math. a number or algebraic symbol prefixed as a multiplier to a variable or unknown quantity (Ex.: x in x(y+z),6 in 6ab)
3. Physics a number, constant for a given substance, used as a multiplier in measuring the change in some property of the substance under given conditions: the coefficient of expansion

Origin: co- + efficient: orig. an adj. meaning “cooperating”