Estonian locative system

The Estonian language has six locative cases, descended from the locative cases of Proto-Finnic. They can be classified according to a three-way contrast of entering, residing in, and exiting a state, with two sets of cases: inner and outer.

For some nouns, there are two forms of the illative: the regular suffix -sse (e.g. keelesse), added to the genitive stem, and an alternative, short form, which is either consists of a different suffix (keel > keelde), lengthening (e.g. maja > majja, [ko:l] > [ko::li]), and/or another change in the word. The always regular -sse illative ending is a newer innovation, and can sometimes have a slightly different meaning than the old "short form" illative, the latter having the concrete locative meaning (e.g.: tuppa 'into the room'), and the former being used in other structures that require the illative (mis puutub toasse 'concerning the room...').[1]