A case is an inflection of nouns, adjectives, pronouns, numerals, infinitives, participles, and adverbs. Many cases are similar in function to English prepositions. In Finnish, there are 15 cases which can be divided into five groups, each of which consists of three cases. Basic cases include nominative, genitive, and accusative, general local cases include partitive, essive, and translative, interior local cases include inessive, elative, and illative, exterior local cases include adessive, ablative, and allative, and means cases include abessive, comitative, and instructive. In addition, there is also a lot of adverbial cases whose usage is limited to a small number of words. Therefore, these forms are usually regarded as adverbs.
Case suffixes cannot usually be added directly to the nominative stem, but a word stem is affected by several changes, the most important of which are consonant gradation and vowel change i ~ e. With the aid of inflectional stems, the formation of cases is much easier, because cases requiring the same inflectional stem can be learnt simultaneously, and the only varying thing is just the case ending.
Inflectional stems include
A good knowledge of inflectional stems is a major requirement for forming Finnish cases.
Finnish cases include