tähtuse
Tähtuse is a term used in Estonian linguistics. It refers to the grammatical phenomenon of vowel harmony within a word. Specifically, it describes the tendency for vowels within a single word to belong to the same class, either front vowels (e, i, ö, ü) or back vowels (a, o, u). This is a common feature in Finnic languages, including Estonian.
The concept of tähtuse helps explain patterns in Estonian grammar, particularly in the formation of word stems