This case is primarily used to show a possessive relationship between two people or things. This case case expresses "whose" or "of what." The noun, in this case, is the person or the thing that "possesses" or "has" another person or thing. In English, this relationship is indicated with an apostrophe "s", with the use of the preposition "of", or with the phrase "belonging to." This case is also used to indicate the object of certain prepositions. The definite and indefinite articles undergo a change in this case.