Funnily, this is how Hungarian appends suffixes at the end of the words. The "brightness" of the suffix has to match the brightness of the stem. We'd call e/i/

Funnily, this is how Hungarian appends suffixes at the end of the words. The "brightness" of the suffix has to match the brightness of the stem. We'd call e/i/ö/ü "high" tone class while a (as in the word calm) / o / u "low" tone.