coefficient of X

coefficient of X
 n.

   Hackish speech makes heavy use of pseudo-mathematical metaphors. Four
   particularly important ones involve the terms coefficient, factor,
   index of X, and quotient. They are often loosely applied to things you
   cannot really be quantitative about, but there are subtle distinctions
   among them that convey information about the way the speaker mentally
   models whatever he or she is describing. Foo factor and foo quotient
   tend to describe something for which the issue is one of presence or
   absence. The canonical example is {fudge factor}. It's not important
   how much you're fudging; the term simply acknowledges that some
   fudging is needed. You might talk of liking a movie for its silliness
   factor. Quotient tends to imply that the property is a ratio of two
   opposing factors: "I would have won except for my luck quotient." This
   could also be "I would have won except for the luck factor", but using
   quotient emphasizes that it was bad luck overpowering good luck (or
   someone else's good luck overpowering your own). Foo index and
   coefficient of foo both tend to imply that foo is, if not strictly
   measurable, at least something that can be larger or smaller. Thus,
   you might refer to a paper or person as having a high bogosity index,
   whereas you would be less likely to speak of a high bogosity factor.
   Foo index suggests that foo is a condensation of many quantities, as
   in the mundane cost-of-living index; coefficient of foo suggests that
   foo is a fundamental quantity, as in a coefficient of friction. The
   choice between these terms is often one of personal preference; e.g.,
   some people might feel that bogosity is a fundamental attribute and
   thus say coefficient of bogosity, whereas others might feel it is a
   combination of factors and thus say bogosity index.