Commonly encountered cases include nominative, accusative, dative and genitive. A role that one of those languages marks by case is often marked in English with a preposition. For example, the English prepositional phrase with (his) foot (as in “John kicked the ball with his foot”) might be rendered in Russian using a single noun in the instrumental case, or in Ancient Greek as τῷ ποδί (tôi podí, meaning “the foot”) with both words (the definite article, and the noun πούς (poús) “foot”) changing to dative form.
More formally, case has been defined as “a system of marking dependent nouns for the type of relationship they bear to their heads“.[5]: p.1 Cases should be distinguished from thematic roles such as agent and patient. They are often closely related, and in languages such as Latin, several thematic roles are realised by a somewhat fixed case for deponent verbs, but cases are a syntagmatic/phrasal category, and thematic roles are the function of a syntagma/phrase in a larger structure. Languages having cases often exhibit free word order, as thematic roles are not required to be marked by position in the sentence.
