Gradation of Nouns

Gradation does not occur in all word stems. Many words only change their endings and markers when declined or conjugated.
In order to determine whether a word is gradational or not, three forms of the noun, the nominative, genitive and partitive, must be compared.
Estonian nouns change either from the strong grade to the weak, or from the weak grade to the strong.

In the case of words that change from the strong grade to the weak, the nominative is in the strong, the genitive in the weak, and the partitive in the strong grade.
kapp; kapi; kappi

In the case of words that change from the weak grade to the strong, the nominative is in the weak, the genitive in the strong and the partitive in the weak grade.
mõte; mõtte; mõtet

The nominative and partitive always take the same grade.

Quantity alteration occurs when the length of the stem sounds is changed. Many words with quantity alteration do not reveal the quantity change in their spelling.

SG : WG : SG                                                  
kool : kooli : kooli
koer : koera : koera
silm : silma : silma

WG: SG: WG
pinge : pinge : pinget
võõras : võõra : võõrast
kallis : kalli : kallist

Quality alteration occurs when plosives or the s sound are present in the strong grade, and absent in the weak grade.

Assimilation occurs when the plosive or s becomes the same sound as the preceding voiced consonant.

Assimilation occurs when the plosive or s becomes the same sound as the preceding voiced consonant.

Quality Alteration. Loss

In the case of loss, the k, t, b, d, g, s sounds in the weak stem 1) disappear.

2) are replaced by other sounds.