konsonanttigraduaatio
Konsonanttigraduaatio is a morphophonological process found in Finnic languages, most notably Finnish, in which stem-internal consonants alternate between two phonological realizations across different inflectional forms. The two realizations are typically described as the strong grade and the weak grade. The alternation concerns the consonant of the stem and is triggered by suffixal contexts rather than by isolated vowel changes; it is a systematic part of the word’s inflectional paradigm rather than a random irregularity.
The exact mapping between grades varies by word, dialect, and part of speech, but the general idea
From a typological perspective, consonant gradation is a central feature of Finnic morphophonology and reflects historical
See also: Finnish phonology, vowel gradation, Finnic languages.