The Noun: Case
The Category of a noun expressing relation between the thing denoted by the noun and other things, properties or actions; Noun cases are the grammatical way in which authors show how nouns or pronouns relate to other words in a sentence. When
There are five cases in English Language—Nominative, Objective, Possessive, Dative and Vocative. But in modern English Grammar; Dative is included in Objective. Hence there are four cases in English Language, such as;
 When a noun (or pronoun) is used as the Subject of a Verb, it is said to be the OBJECTIVE CASE, such as; Mr. Ali threw a stone. [Who threw a stone = Mr. Ali (subject)]
 When a Noun (or pronoun is used as the Object of a verb, it is said to be in the OBJECTIVE CASE, as such; Mr. Ali threw a ball. Ahmad bowled him out.
[What did Mr. Ali throw? = a ball (object)]
The horse kicked the boy.
[Whom did the horse kick? = a boy. (Object)]
Note: To find the Nominative put who? /What? Before the verb and to find the Objective put whom? / What? Before the verb so the Nominative generally comes before the verb and the Objective after it.
 THE POSSESSIVE CASE denotes ownership or possession or relationship or authorship. The possessive answers the question –‘Whose?’, as such;
This is Kamal`s umbrella. (Possession)
These are Mirza Adeb`s plays. (Authorship)
A mother`s love is a noble thing. (Relationship)
 The VOCATIVE CASE is practically a nominative of address, such as;
Come here, Ali.
Come on, boys.
Note: The forms of Nouns remain the same in the Nominative Case, Objective Case and Vocative case. But the form is changed only in the Possessive Case.
FORMATION OF THE POSSESSIVE CASE
The rules are:
When the noun denotes the name of a living one, apostrophe [`s] or only apostrophe comma [`] with out’s; is used.
(a) When such a Noun is singular, The possessive case is formed by adding [`s] to the noun: as such;
The boy`s pen
Note: The letter [s] is omitted and only the apostrophe comma is used in a few words where too many hissing sounds would come together: as such;
For justice` sake;
For goodness` sake;
For conscience` sake;
For Moses` Laws;
However, we can add either apostrophe comma [`] or `s in such cases, as such;
Keats’s poem (or, Keats`s poem), Ali`s car (or Ali`s car)
(b) When the Noun is Plural and ends in [s], the Possessive Case is formed by adding only an apostrophe comma: as such;
(c) When the Noun is Plural but does n`t end in s, the Possessive Case is formed by adding , as such;
USE OF POSSESSIVE CASE
(a) The possessive [`s] , is chiefly used with the names of Living Things. It can`t be used with the names of inanimate things, as such;
The boy`s hand;
The girl`s hair;
The leg of the chair [Not, the chair`s leg]
The cover of the book [Not, the book`s cover]
The roof of the house [Not, the house`s roof]
Of course, [of] instead of [`s] may be used in both the cases [Living & non-living], as such;
The leg of the boy
The leg of the chair
(b) The possessive [`s] is used with the personified objects, as such;
(c) The possessive [`s] is also used with the nouns denoting time, space or weight, as such;
A day`s match;
A week`s holiday;
Next year`s prices;
Last night`s TV programme
(d) The noun following a Possessive Case can be left out when we talk about someone`s home, some shops and services, as such;
We are going to Ali`s (home) this evening.
Are you going to the butcher`s (shop)?
Who’s batting is this? Ali`s (batting)
(e) When the Noun is a long phrase, we use [of] instead of [`s], as such;
He is the brother of someone who used to give us chocolates.
NOUN IN APPOSITION
Read the following sentences:
Imran Khan, our captain, made fifty runs.
Here ‘Imran Khan’ and ‘our captain’ mean the same person. Hence ‘our captain’ is in Apposition to Imran Khan. Such Apposition is placed just after the noun. [Apposition means ‘placing near’]
A noun in Apposition is in the same case as the Noun which it explains.