Thanks, that article does clear it up. So the orbit doesn't change shape nor does it shift, instead it rotates (from the article: "More precisely, it is the gra

Thanks, that article does clear it up. So the orbit doesn't change shape nor does it shift, instead it rotates (from the article: "More precisely, it is the gradual rotation of the line joining the apsides of an orbit"—so I guess the ellipse major axis rotates). From what I can tell using precession as a direct substitute for rotation is less common, even in astronomy—but maybe I've just had poor samples so far. I was thinking of it as: "Precession is a change in the orientation of the rotational axis of a rotating body." (https://en.wikipedia.org/wiki/Precession https://en.wikipedia.org/wiki/Precession)