In grammar, the comitative case (abbreviated ) is a grammatical case that denotes accompaniment. In English, the preposition "with", in the sense of "in company with" or "together with", plays a substantially similar role. Other uses of "with", like in the meaning of "using" or "by means of" (I cut bread with a knife), correspond to the instrumental case or related cases.
Core meaning
The comitative case encodes a relationship of "accompaniment" between two participants in an event, called the "accompanier" and the "companion". In addition, there is a "relator" (which can be of multiple lexical categories, but is most commonly an affix or adposition). This Italian sentence is an example:
:<nowiki>[</nowiki>il professore<nowiki>]</nowiki><sub>accompanier</sub> entra nell'aula <nowiki>[</nowiki>con<nowiki>]</nowiki><sub>relator</sub> <nowiki>[</nowiki>i suoi studenti<nowiki>]</nowiki><sub>companion</sub>
:<nowiki>'the professor enters the lecture-hall (together) with his students'</nowiki>. Enrique Palancar defines the role of Instrumental case as <nowiki>'the role played by the object the Agent manipulates to achieve a change of state of the Patient.'</nowiki> Even though the difference is straightforward, because the instrumental and the comitative are expressed the same way in many languages, including English, it is often difficult to separate them.
Russian is one of many languages that differentiate morphologically between instrumental and comitative: