Pronoun agreement is a common problem for those who want to speak and write properly. There is also a problem brought about by concerns with language being sexist, so the pronoun "he" is no longer commonly used. Fortunately, with some information and tips, you can resolve these problems.
In most cases, a pronoun refers back to a noun that appeared previously in the text or conversation. That noun is called the antecedent of the pronoun and the noun and pronoun must agree as to whether they are singular or plural. Let us look at some of the problem areas of pronouns and their usage, including indefinite pronouns, gender issues, subject pronouns, and object pronouns.
The indefinite pronouns: nobody, anybody, everybody, somebody, anyone, everyone, someone, no one, something, anything, everything, and nothing are always singular.
This is one of the main rules for pronoun agreement. Examples would be: "Anyone can do this if he tries." or "Everybody is smart in his own way."
Gender issues continue to plague our society right now. It was widely understood that words like: man, he, and him, could stand more both sexes. Using "he or she" can become cumbersome, so some use "he/she." It would be a lot easier to go back to using "he" and "him" and not worry about offending anyone. Because of this problem, many people use "them" and "their" incorrectly.
Since this sentence is wrong "Somebody has left their bag here" and "Somebody has left his bag here" is right grammatically but not acceptable, some people have come up with a solution.
There is a movement to allow the word "their" to be a gender-free, singular pronoun. This would be good because that is what most people are doing to avoid writing "he or she." For now, a way around this problem is to use a plural subject. That way you can use "their" all you want.
One of the hardest parts of pronoun agreement is determining whether the noun being replaced is a subject or an object.
Subject pronouns are: he, she, I, we, they, who, whoever, you, and it. Compound subjects can confuse but you need to remember that each individual subject needs the subject form, like "My sister and I went to the store." and "The person who spilled the milk needs to clean it."
Object pronouns are: him, her, me, us, them, whom, whomever, you, and it. Examples are: "The ball came towards Jack and me", "Sandra does not like him or me." and "You may invite whomever you wish."
One final tip: A pronoun refers to a noun and that relationship needs to be clear. Watch out for compound nouns so the pronoun does not confuse the reader.