In grammar, the sociative case is a grammatical case in the Hungarian, Tamil, and Malayalam languages that can express the person in whose company (cf. Latin socius) an action is carried out, or to any belongings of people which take part in an action (together with their owners).
In Hungarian, this case is denoted by the suffixes -stul and -stül, depending on vowel harmony. This case is archaic and nowadays the instrumental-comitative case is usually used instead. Nevertheless, it can be used also in modern Hungarian to express a slight pejorative tone against a person. Here are a few examples:
The use of the sociative case kölyköstül ("with her kids") signifies the speaker's contempt. The case appears also in some commonly used expressions, which survived the general obsolescence of the sociative case:
In Tamil, the sociative case takes the endings -ஓடு (-ōṭu) or -உடன் (-uṭan). It is related to the instrumental case but not identical to it. In contrast to the sociative case, the instrumental case usually denotes the means of action and takes the ending -ஆல் (-āl).