Grammatical Case refers to a set of forms related to a noun's or pronoun's grammatical function (i.e. job) in a sentence.
Here's a quick recap of those two using the noun poet.
Refers to singular and plural - a set of forms which conveys meanings of oneness (e.g. poet) and manyness (e.g. poets).
Consists of masculine, feminine, common, neuter forms - this form-set conveys meanings of maleness (as in poet) or femaleness (as in poetess).
Case is a third set of forms and the most important.
Case is that form of a noun (or pronoun) which tells us about it's grammatical function in a sentence.
Note there are forms and functions.
Can you notice the different forms of the first person pronoun I and the noun poet in the two sets of sentences below?
I, me, and mine are different forms of the first person pronoun I and poet, and poet's are different forms of the noun poet.
These different forms illustrated above are associated with different functions in sentences.
I is used for the subject and me for the object.
You cannot say...
I, me, mine and poet, poet's are called Case forms. These forms signal to us the functions performed by nouns and pronouns in sentences.
So what you have to do boils down to...
learning the forms and their associated functions.
In English, there is no one-to-one correspondence between forms and functions. See the word poet performing two functions in the sentences we have seen above.
There are five cases in English...but all of them do not have unique sets of forms today.
So, you end up having three sets of forms for the pronouns and two for the nouns!
They are as follows:
|nominative case||accusative case||genitive case|
In modern English...
used for the following functions:
used for these functions:
is used for showing:
is used for the indirect object of a ditransitive verb.
is used when we address someone.
What is important in grammar is to learn first the different forms and then the functions associated with those forms.
Grammatical Case is expecially important because it relates to the noun's syntax, i.e. its relationship with other words in a sentence.