Pronouns

Definition

A pronoun (I, me, he, she, herself, you, it, that, they, each, few, many, who, whoever, whose, someone, everybody, etc.) is a word that takes the place of a noun. In the sentence Joe saw Jill, and he waved at her, the pronouns he and her take the place of Joe and Jill, respectively. There are three types of pronouns: subject (for example, he); object (him); or possessive (his).
Rule 1. Subject pronouns are used when the pronoun is the subject of the sentence. You can remember subject pronouns easily by filling in the blank subject space for a simple sentence.

Example: ___ did the job.
I, he, she, we, they, who, whoever, etc., all qualify and are, therefore, subject pronouns.

Rule 2. Subject pronouns are also used if they rename the subject. They will follow to be verbs, such as is, are, was, were, am, will be, had been, etc.

Examples:
It is he.
This is she speaking.
It is we who are responsible for the decision to downsize.

NOTE

In informal English, most people tend to follow to be verbs with object pronouns like me, her, them. Many English scholars tolerate this distinction between formal and casual English.

Example: It could have been them.

Technically correct: It could have been they.

Example: It is just me at the door.

Technically correct: It is just I at the door.

Rule 3. This rule surprises even language watchers: when who refers to a personal pronoun (I, you, he, she, we, they), it takes the verb that agrees with that pronoun.

Correct: It is I who am sorry. (I am)

Incorrect: It is I who is sorry.

Correct: It is you who are mistaken. (you are)

Incorrect: It is you who's mistaken.

Rule 4. Object pronouns are used everywhere else beyond Rules 1 and 2 (direct object, indirect object, object of a preposition). Object pronouns include me, him, herself, us, them, themselves, etc.

Examples:
Jean saw him.
Him is the direct object.

Give her the book.
Her is the indirect object. The direct object is book.

Are you talking to me?
Me is the object of the preposition to.

Rule 5. The pronouns who, that, and which become singular or plural depending on the subject. If the subject is singular, use a singular verb. If it is plural, use a plural verb.

Example: He is the only one of those men who is always on time.
The word who refers to one. Therefore, use the singular verb is.

Sometimes we must look more closely to find a verb's true subject:

Example: He is one of those men who are always on time.
The word who refers to men. Therefore, use the plural verb are.

In sentences like this last example, many would mistakenly insist that one is the subject, requiring is always on time. But look at it this way: Of those men who are always on time, he is one.
Rule 6. Pronouns that are singular (I, he, she, everyone, everybody, anyone, anybody, no one, nobody, someone, somebody, each, either, neither, etc.) require singular verbs. This rule is frequently overlooked when using the pronouns each, either, and neither, followed by of. Those three pronouns always take singular verbs. Do not be misled by what follows of.

Examples:
Each of the girls sings well.
Either of us is capable of doing the job.
Neither of them is available to speak right now.

Exception: When each follows a noun or pronoun in certain sentences, even experienced writers sometimes get tripped up:

Incorrect: The women each gave her approval.
Correct: The women each gave their approval.
Incorrect: The words are and there each ends with a silent vowel.
Correct: The words are and there each end with a silent vowel.

These examples do not contradict Rule 6, because each is not the subject, but rather an adjunct describing the true subject.

Rule 7. To decide whether to use the subject or object pronoun after the words than or as, mentally complete the sentence.

Examples:
Tranh is as smart as she/her.
If we mentally complete the sentence, we would say Tranh is as smart as she is. Therefore, she is the correct answer.

Zoe is taller than I/me.
Mentally completing the sentence, we have Zoe is taller than I am.

Daniel would rather talk to her than I/me.
We can interpret this sentence in two ways: Daniel would rather talk to her than to me. OR Daniel would rather talk to her than I would. A sentence's meaning can change considerably, depending on the pronoun you choose.

Rule 8. The possessive pronouns yours, his, hers, its, ours, theirs, and whose never need apostrophes. Avoid mistakes like her's and your's.
Rule 9. The only time it's has an apostrophe is when it is a contraction for it is or it has. The only time who's has an apostrophe is when it means who is or who has. There is no apostrophe in oneself. Avoid "one's self," a common error.

Examples:
It's been a cold morning.
The thermometer reached its highest reading.
He's the one who's always on time.
He's the one whose wife is always on time.
Keeping oneself ready is important.

Rule 10. Pronouns that end in -self or -selves are called reflexive pronouns. There are nine reflexive pronouns: myself, yourself, himself, herself, itself, oneself, ourselves, yourselves, and themselves.
Reflexive pronouns are used when both the subject and the object of a verb are the same person or thing.

Example: Joe helped himself.

If the object of a preposition refers to a previous noun or pronoun, use a reflexive pronoun:

Example: Joe bought it for himself.

Reflexive pronouns help avoid confusion and nonsense. Without them, we might be stuck with sentences like Joe helped Joe.

Correct: I worked myself to the bone.

The object myself is the same person as the subject I, performing the act of working.

Incorrect: My brother and myself did it.
Correct: My brother and I did it.

Don't use myself unless the pronoun I or me precedes it in the sentence.

Incorrect: Please give it to John or myself.
Correct: Please give it to John or me.
Correct: You saw me being myself.

Myself refers back to me in the act of being.
A sentence like Help yourself looks like an exception to the rule until we realize it's shorthand for You may help yourself.
In certain cases, a reflexive pronoun may come first.

Example: Doubting himself, the man proceeded cautiously.

Reflexive pronouns are also used for emphasis.

Example: He himself finished the whole job.

Rule 11a. Avoid they and their with singular pronouns.

Incorrect: Someone brought their lunch.
Correct: Someone brought her lunch.
OR
Someone brought his lunch.

If the gender is undetermined, you could say Someone brought his or her lunch (more on this option in Rule 11b).
Rule 11b. Singular pronouns must stay singular throughout the sentence.

Incorrect: Someone has to do it—and they have to do it well.

The problem is that someone is singular, but they is plural. If we change they to he or she, we get a rather clumsy sentence, even if it is technically correct.

Technically correct: Someone has to do it—and he or she has to do it well.

Replacing an ungrammatical sentence with a poorly written correction is a bad bargain. The better option is to rewrite.

Rewritten: Someone has to do it—and has to do it well.

Many writers abhor the he or she solution. Following are more examples of why rewriting is a better idea than using he or she or him or her to make sentences grammatical.

Incorrect: No one realizes when their time is up.
Correct but awkward: No one realizes when his or her time is up.
Rewritten: None realize when their time is up.
Incorrect: If you see anyone on the trail, tell them to be careful.
Correct but awkward: If you see anyone on the trail, tell him or her to be careful.
Rewritten: Tell anyone you see on the trail to be careful.

Rule 12. When a pronoun is linked with a noun by and, mentally remove the and + noun phrase to avoid trouble.

Incorrect: Her and her friend came over.

If we remove and her friend, we're left with the ungrammatical Her came over.

Correct: She and her friend came over.

Incorrect: I invited he and his wife.

If we remove and his wife, we're left with the ungrammatical I invited he.

Correct: I invited him and his wife.

Incorrect: Bill asked my sister and I.

If we remove my sister and, we're left with the ungrammatical Bill asked I.

Correct: Bill asked my sister and me.

NOTE

Do not combine a subject pronoun and an object pronoun in phrases like her and I or he and me. Whenever and or or links an object pronoun (her, me) and a subject pronoun (he, I), one of those pronouns will always be wrong.

Incorrect: Her and I went home.
Correct: She and I went home. (She went and I went.)

http://www.grammarbook.com/grammar/pronoun.asp