Noun cases refer to how a noun is used in a sentence, such as a subject, direct object, or possessive. Although there is some variation between cases among languages, many languages use the same noun cases. These cases can be determined by placement in a sentence, a change to the noun's spelling, or both.
There are five noun cases in English. With one exception, the genitive case, the noun cases are determined by the noun's placement in a sentence. Punctuation, prepositions, and conjunctions may also give clues as to the case of a specific noun. The simplest of these cases is the vocative case, which is used only when a noun stands apart from a sentence, such as in "Jake, the laundry is done" or simply, "Jake!" Nouns in the vocative case appear alone or are separated by a comma.
The genitive, or possessive, case is the only noun case in English that requires a spelling change. This case signifies ownership of something and is indicated by an apostrophe "s" for singular ownership or an "s" apostrophe for plural ownership. For example, "the dog's owner," indicates a single dog, but "the dogs' owner" indicates multiple dogs.
The subjective, or nominative case, is used when the noun is the subject of the sentence. Nominative nouns occur at the beginning of simple sentences and are located near the main verb. These nouns name what is performing the action. For example, in the the simple sentence, "The dog barked" and the complex sentence, "Running down the road, the dog barked," the noun "dog" is the subject of both.
The objective, or accusative, case is used when the noun is the direct object of the sentence. Direct objects are nouns to which the action is happening. For example, in the sentence, "She drove her car," the noun "car" is the direct object because the action of driving was being performed on the car. Direct objects usually appear after the verb.
The dative case applies to indirect objects. Indirect objects are affected by the action of the sentence but are not what the verb is acting upon. For example, in the sentence "Jake gave a piece of cake to Jill," what Jake gave, the piece of cake, is the direct object, and the person he gave the cake to, Jill, is the indirect object.
Other languages may include spelling changes, usually to the end of the word, or may have additional, or fewer, cases. The Russian language, for instance, includes a sixth case, the instrumental, which is used to indicate how something was done. For example, in the sentence, "She colored the picture with crayons," the word "crayons" would be in the instrumental case.