I am having some difficulty understanding the meaning of the "Q factor." One definition is that it is the ratio of the reactance to the resistance. This perplexes me, because for an RLC circuit, this is zero at resonance!

Let's take the example of a non-ideal inductor (in my application I am actually attaching this to a MEMS pressure sensor to create a wireless pressure sensor). It is an inductor in series with a resistor, all in parallel with a cap. What is the "quality factor" of this circuit? Is this even meaningfull without a "load capacitance" also added in? The definition I have found involves a formula like 1/R * sqrt(L/C).. but this does not make sense given the earlier definition of reactance to resistance, which is zero at resonance.

Thanks in advance and I apologize for the open-endedness of my question. Really been banging my head over this one for a while.