Disclaimer: The use of third-person pronouns in English is evolving: "they/their/them" as a third person singular is widely used and accepted in spoken and written English. HOWEVER, formal written English takes time to catch up with these changes. Therefore, you are encouraged and often expected, to use the traditional versions (see below) in academic writing.
Pronouns are words such as me, you, he, she, it, we, and they that we frequently use so that we do not have to constantly write out the name of some person, place, or thing.
There are several things to remember when using pronouns:
Pronouns must clearly refer to their antecedents
The antecedent is the person, place, or thing that the pronoun refers to. For example, in the following sentence the pronoun "she" refers to the antecedent "Elizabeth"
Elizabeth decided that she was not going to give in to the kidnapper's demands.
Sometimes there is confusion over what the pronoun's antecedent actually is:
Bob and his best friend built a tree house in his yard.
The possessive pronoun his in "his best friend" does have a clear antecedent (Bob), but the pronoun in "his yard" could refer to either Bob or the friend; thus, it is confusing. The best solution is to rewrite the sentence.
Example: Bob and his friend built a tree house in Bob's yard.
Pronouns must agree with their antecedents
If you were referring to the antecedent "Mary," you would not use the pronoun "him" or "them" because it would not make sense.
INCORRECT: Mary finally got what was coming to him. Or... Mary finally got what was coming to them.
"Him" refers to a male, and Mary is presumably female. Likewise, "them" refers to more than one person, and Mary is only one person. The correct choice would be "her," which refers to one female person.
Sometimes, usually when the gender of the antecedent is unclear, writers choose a pronoun that does not agree with its antecedent, as in the following sentence:
INCORRECT: It is important for a doctor to keep their patients' records confidential.
The possessive pronoun "their" is supposed to refer to more than one person, but in this sentence, its antecedent is one person (a doctor). The problem occurs because we do not know whether the doctor is male or female. NOTE: Because a doctor might be female, it is considered sexist to say "his":
INCORRECT (sexist): It is important for a doctor to keep his patients' records confidential.
One solution is to use the admittedly awkward option of "his or her":
CORRECT (but awkward): It is important for a doctor to keep his or her patients' records confidential.
A better solution is to make the antecedent plural so the pronoun "their" can remain:
CORRECT: It is important for doctors to keep their patients' records confidential.
Another acceptable solution is to rewrite the sentence to avoid the pronoun altogether:
CORRECT: It is important for doctors to keep all patient records confidential.
Indefinite words anybody, anyone, everybody, everyone, nobody, no one, somebody, someone, and each are considered singular; thus, we cannot use "they," "their," or "them" in reference to one of them.
INCORRECT: Everybody ran to their cars and drove away.
The same solutions apply: change the pronoun, change the antecedent, or rewrite the sentence.
CORRECT: Everybody ran to his or her car and drove away.
CORRECT: All of the people ran to their cars and drove away.
CORRECT: Everybody ran to the parking lot and drove away.
There are two pronoun cases, subjective and objective. When the pronoun in the subject of a clause, we use subjective case; otherwise, we use the objective case.
Subjective pronouns: I, you, he, she, it, we, and they.
Objective pronouns: me, you, him, her, it, us, and them.
Most of the time, choosing the correct pronoun case is simple. For example, you wouldn't write "Me went to the store" or "Give the ball to they" because it sounds wrong. Clearly, it should be "I went to the store" and "Give the ball to them."
Yet for some reason, when the pronoun is paired with a noun, the correct choice becomes harder to distinguish.
Examples: She/Her and Joe went to the prom. Or...We decided to throw a party for Sue and he/him.
The easiest way to decide which pronoun to use is to pretend that the other person is not there.
Example: If Joe was not there, the choice would be simple: "She went to the prom."
Thus the correct answer is "She and Joe went to the prom."
Likewise, because we would always say "We decided to throw a party for him," we should also say "We decided to throw a party for Sue and him."