Estonian grammar is the grammar of the Estonian language.

Inflectional endings as listed below are added to the stem of a noun, which is formed from:

Singular nominative, singular genitive and singular partitive are not predictable and have to be taken from the vocabulary (gradation may also apply).

Singular genitive always ends in vowel. When formed from a stem that ends in consonant, it can take the following endings: -a, -e, -i, -o, -u.

Singular partitive can take the following endings: -d, -t, -a, -e, -i, -u.

Plural partitive is formed from either singular genitive or singular partitive and can take the following endings (some words have two forms):

Singular illative has a short form in some words. It can take the following endings: -de, -he, -hu, -a, -e, -i, -u. In case it takes the vowel ending, this vowel is the same as the ending vowel of the singular genitive form of the given word, but the vowel (if it is already long or a diphthong) or its preceding consonant (if the vowel is short and the consonant either short or long) is lengthened to the third degree and thus becomes overlong. If illative ends with -sesse, then the short form is -sse.

Plural illative, inessive, elative, allative, adessive, ablative, translative have a short form in some words. If the plural partitive ends with -id, then the short plural stem is this form without -d (instead of plural genitive with -de-); if it ends with a vowel, then the short plural stem is this form; if it ends with -sid, then the short plural cannot be formed.