When Bad Grammar Happens to Good People A Lesson on Pronoun Cases Personal pronouns and a couple of relative pronouns vary in form according to person and number (as discussed in the Grammar Review) and according to case as well. The three cases are the subjective case (sometimes called the nomina- tive case), the objective case, and the possessive case. You choose between them according to the role you're asking the pronoun to take on in a sentence. For a basic illustration, let's say you're referring to your- self and your ownership of a book. You might say I own that book or That book belongs to me or That book is mine. In those three sentences we used the first-person singular pro- nouns "I," "me," and "mine." In each instance, of course, you're referring to yourself, but the form of the pronoun you use to do it changes. In the first sentence, I own that book, you are the