How do you decide which form of a pronoun to use, as in the choices of the wording in “John is as fast as him” and “John is as fast as he”? Knowing the varieties of pronouns will help you choose the correct form.
A subject pronoun is one used as the subject of a sentence, as in “He is right” or “I am amazed.” (Subject pronouns include I, you, he, she, it, we, and they.) Subject pronouns may also rename the subject, following a copular verb (one that is a form of “to be”): “It is I who left the chair there.”
A subject pronoun should also be used for such sentences as “It might have been she,” though an object pronoun is used in its place almost invariably in casual speech and often in writing.
Object pronouns (me, you, him, her, it, us, and them), by contrast, are used to identify the object of a sentence, as in “Mary gave it to her” and “The tourists went to see them.” (Notice that you and it can serve as both subject and object pronouns.) Object nouns are used with all the three types of objects: “The Smiths invited us” (direct object), “The Smiths gave us our dish back” (indirect object), and “The Smiths gave a party for us” (object of a preposition).
Should a sentence read, “I am older than her” or “I am older than she”? In a statement of comparison that uses as or than and does not end with a copular verb, temporarily add one to test the correct type of pronoun: “I am older than her is” does not sound right, but “I am older than she is” does, so the correct word in this sentence is she. (Therefore, the correct sentence in the pair of examples in the first paragraph of this post — in formal writing, at least — is “John is as fast as he.”)
Note, however, that what appears to be a sentence with an incorrect form of a pronoun can be correct when it means something else. For example, “She fell asleep before him” could mean that the woman fell asleep in front of someone, not earlier than someone, in which case the statement is correct.
What if the sentence refers to more than one person? Several factors come into play. The pronoun in “Joe and I were invited to the party” is correct because I is part of the subject (“Joe and I”). But “John went to the party with Joe and I” is not, because “Joe and I” is now the object, and the correct personal pronoun for an object is me: “John went to the party with Joe and me.” (Test for the correct form of the pronoun by removing the other person from the object: “John went to the party with me,” not “John went to the party with I,” is correct, so “John went to the party with Joe and me” is correct.)
But an exception is made when the reference to Joe and the writer is preceded by a copular, or linking, verb (a form of “to be”), as in “The last people at the party were Joe and I.” In this sentence, “Joe and I” are predicate nominatives, meaning that they rename or describe the subject: “Joe and I” equals “the last people at the party.”
A pronoun in a predicate nominative takes the subjective, not objective, case: “The last people at the party were Joe and I” is correct. It may seem wrong, but that’s because the rule is ignored in most spoken English and in much written English as well, so we’re accustomed to hearing and reading the error. It should be observed, however — at least in formal English. (Some comments on this post refer to a previous version of this discussion.)
Possessive pronouns (mine, yours, his, hers, its, ours, and theirs) signal possession or relationship and, unlike nouns in possessive form, never include apostrophes. They take the same form whether in the subjective position or the objective position: “That is hers. Yours is here.”
Reflexive pronouns (myself, himself, herself, itself, themselves, ourselves, yourself, and yourselves) refer to something already mentioned (“The machine appeared to start by itself”) or implied (Suit yourselves”). “The directions applied only to myself” is wrong because the person indicated by myself is not explicitly or implicitly referred to. (The correct wording is “The directions applied only to me.”) However, “I followed the directions myself” is correct because myself refers to the subject I.