Grammar for Everyone - Barbara Dykes 2007

24 Case - Nominative
Introduction
Part II The parts of speech

Case is the term for a system of categorising nouns or pronouns according to their function in a sentence or clause. The system is very simple and provides clarity and a means of revising, as well as the important function of enabling better understanding of certain foreign languages.

Simply, the part that a noun or pronoun plays in a sentence gives it its case.

Nominative

The subject of a verb is in the nominative case, for example:

The taxi is here.

We are going to the theatre.