Is there a term for the ratio of a function and its derivative?
Given a function $f(x)$ and its derivative $f'(x)$, is there a term for $\frac{f(x)}{f'(x)}$ or for $\frac{f'(x)}{f(x)}$?
Certainly the latter one is called the logarithmic derivative: $$\frac{d\log(f(x))}{dx} = \frac{f'(x)}{f(x)}$$