As you may have noticed, above you will find words for "The principle, which links geometrical optics (or "ray optics") with wave optics, that the path traversed by a ray between two given points is: (in the original "strong" formulation) the one that takes the least time, or (in a weaker but more general formulation) one that takes a time that is "stationary" with respect to variations of the path (so that, loosely speaking, a small change in the ray path entails a very small change in the traversal time).". Hover the mouse over the word you'd like to know more about to view its definition. Click to find a better fitting word. Finally, thanks to ChatGPT, the overall results have been greatly improved.