# Ellipse: Name for the ratio $a/b$?

Given an ellipse with semi-major axis $a$ and semi-minor axis $b$, is there a "common" (or at least standard) name for either $\frac{a}{b}$ or $\frac{b}{a}$?

I keep wanting to (informally) call it the eccentricity, but generally that's the name given to the quantity $\sqrt{1 - \frac{b^2}{a^2}}$. I've seen $1 - \frac{b}{a}$ referred to as the flattening factor.

This seems like a pretty straightforward question, but I can't seem to find an answer. Bonus kudos if you can give me a reference.