Consonant gradation is a linguistic term for the changing of consonants. Consonant changes occur in the declension of both nouns and verbs and they are very characteristic of the Finnish language. Consonant gradation is used to maintain vocal harmony in the language.

Consonants can be changed to different consonants or eliminated altogether. Double consonants can also be changed to single consonants. For example, double consonants kk, pp, tt are often replaced by single k, p, t. E.g. the genitive of lakki 'cap' is lakin. In Finnish, k, p, and t are the only letters affected by consonant gradation.

K is the letter with the most possible changes. Using the change from the nominative to the genitive case as an example:

• It can completely disappear (jalka ~ jalan)
• Double (liike ~ liikkeen)
• The uku/yky pattern can change to uvu/yvy (puku ~ puvun)
• The lki pattern can change to lje (kylki ~ kyljen)
• The rki pattern can change to rje (järki ~ järjen)
• The nk pattern can change to ng (Helsinki ~ Helsingin)

Changes for other letters include t ~ d (tietää ~ tiedän), rt ~ rr (kertoa ~ kerron), and nt ~ nn (antaa ~ annan).

Note: the change in vowels (e.g. Suomi ~ Suomen) is not considered consonant gradation.

External links

Introduction to Finnish - Consonant Gradation (http://www.ddg.com/LIS/InfoDesignF97/paivir/finnish/kptverb.html)
Finnish Grammar - Consonant Gradation (http://www.uta.fi/~km56049/finnish/consgrad.html)