Explain the concept of agreement in case and provide examples.

Agreement in case refers to the grammatical relationship between a noun or pronoun and other words in a sentence, specifically in terms of their case forms. Case is a grammatical category that indicates the function of a noun or pronoun in a sentence, such as subject, object, or possessive.

In English, there are three main cases: nominative (subject), accusative (object), and genitive (possessive). Agreement in case occurs when the case form of a noun or pronoun matches the case form required by the verb or preposition it is associated with.

Here are some examples to illustrate the concept of agreement in case:

1. Nominative case agreement:
- She is a doctor. (The pronoun "she" is in the nominative case as the subject of the sentence.)
- The students are studying. (The noun "students" is in the nominative case as the subject of the sentence.)

2. Accusative case agreement:
- I saw him at the park. (The pronoun "him" is in the accusative case as the object of the verb "saw.")
- They invited us to the party. (The pronoun "us" is in the accusative case as the object of the verb "invited.")

3. Genitive case agreement:
- This is John's car. (The noun "John's" is in the genitive case to indicate possession.)
- The cat's tail is fluffy. (The noun "cat's" is in the genitive case to indicate possession.)

It is important to note that agreement in case can also occur between a noun or pronoun and a preposition. For example:
- The book is on the table. (The noun "table" is in the accusative case after the preposition "on.")
- She went to the store. (The noun "store" is in the accusative case after the preposition "to.")

In summary, agreement in case involves matching the case form of a noun or pronoun with the appropriate case required by the verb or preposition in a sentence. This ensures grammatical accuracy and clarity in expressing the relationships between words.