Most people that study German learn about "stem-changing VERBs (z.B. singen, sang, gesungen).
I don't come across them often, but there appear to be stem-changing adjectives, as well. Example: Gross= great. But Friedrich der Grösse.
Are there "classes" of such adjectives (e.g. for words with a, o, or u)? Or a handful of individual cases? Or am I seeing something that doesn't actually exist?