Double consonant gradation (kk, pp, tt)

Consonant Gradation

Adding an ending like the inessive (-ssa or -ssä) closes the final syllable of a word. This often triggers consonant gradation, where consonants in the root shift from a "strong" grade to a "weak" grade.

The simplest pattern is quantitative gradation, where double consonants weaken to single consonants.

kkk

luokka (classroom) → luokassa (in the classroom)

The teacher is in the classroom.
Opettaja on luokassa.
The old man is in the church.
Vanha mies on kirkossa.

ppp

kauppa (shop) → kaupassa (in the shop)

I am in the shop today.
Minä olen tänään kaupassa.
The book is in the backpack.
Kirja on repussa.

Notice how the subject (kukka) keeps its strong grade kk because it has no ending, while the location (kuppi) takes the inessive ending and weakens to p:

The small flower is in the cup.
Pieni kukka on kupissa.

ttt

teltta (tent) → teltassa (in the tent)

The girl sits in the tent.
Tyttö istuu teltassa.
The small dog is in the hat.
Pieni koira on hatussa.