Sometimes a case called prolative is suggested, with the ending tse appended to the plural stem and corresponding to the English prepositions “through” or “via”. It can be formed from new words, too, e.g. sähköpostitse or (less formally) meilitse “by e-mail”. Most linguists regard tse simply as an adverbial suffix.
Sometimes a case, exessive, with the ending ntA (combined from the nA of essive and tA of partitive) is suggested, meaning “from the role of”, thus making the system of locational cases more orthogonal. It is used in a few dialects, though often in a few words only, e.g. using luonta instead of the adverb luota (which is morphologically a partitive form and is purely locational in meaning). However, such dialects may also use -ntA forms much like case suffixes, e.g. korjattavanta (from the state of being repaired), an “exessive” of the participle korjattava.
Word forms ending with nkaa, with a meaning corresponding to the comitative, i.e. “together with”, exist in some dialects. However, they are explainable as simple contractions: talon kanssa → talonkaa.
In composite words, the first word often undergoes changes: hevonen “horse” and voima “power” yield hevosvoima “horsepower”, as discussed in section Compositive forms. One might argue that this means that there is a separate case, compositive.
A case called lative, with endings such as s and k and a generic locational meaning “to”, has actually existed in the language. It only survives in some adverbs (e.g. ulos) and in peculiar derivations which are between adverbs and cases of nouns in the comparative form, e.g. rannemmas (from ranta “beach, shore” + comparative suffix + ending s); see section Comparison of nouns .
There are several very productive suffixes for deriving adverbs, such as sti, corresponding to the English suffix “ly”, which can be attached to most adjectives, as well as to numerals, e.g. kolmesti “three times”.
However, these forms are normally not regarded as cases. One reason for this is that they cannot have attributes. We can say sähköpostilla “by e-mail, using e-mail” or, with almost the same meaning, sähköpostitse. But only the former can have an attribute, e.g. luotettavalla sähköpostilla “using reliable e-mail”.