All languages have grammatical case. The number of cases varies from one language to another but all have nominative case. This is the subject form of a noun/pronoun. Grammatical case refers to the change in form of a noun/pronoun in a sentence.
English has two cases for nouns and three for pronouns. The cases for nouns are nominative and genitive. For example, the noun "friend" is "friend" in nominative and "friend's" in genitive. Nominative case is for subjects and genitive case is for possession.
Of course English can express many other cases but they are not inflected. Accusative case is used for direct objects but English nouns are the same in nominative and accusative. Dative case is used for indirect objects but this is also indistinguishable from nominative in English. This is illustrated by the following examples:
I want to meet your friend. (accusative)
I gave the ticket to my friend. (dative)
English pronouns have three cases. They are nominative, accusative and genitive. The following sentences illustrate the three cases:
I can play the piano. (nominative)
He doesn't know me. (accusative)
This is my car. (genitive)
The first person singular pronoun has three forms: I, me and my. Another form is "mine," a possessive pronoun, but this can also be analyzed as genitive.
Many languages have more inflected cases than English. German pronouns have four (nominative, accusative, dative, genitive) and Russian has six (nominative, accusative, dative, genitive, instrumental, locative).
Instrumental case indicates the manner in which an action is performed. For example, in the sentence "He kicked the ball with his left foot," the noun "foot" is in instrumental case.
Locative case is used for location. In the sentence "They live in Vancouver", the city "Vancouver" is in locative case.
Another case found in a number of languages is vocative. This is used to address people. In the question "Julius, how are you?" the name "Julius" is in vocative case.
Case is an important feature of grammar. Found in every language, it is thus universal. However, the number of cases can vary significantly from one language to another. English nouns are inflected for two cases, Russian for six, Finnish for fifteen and Hungarian for eighteen.