Agreement
Agreement means consistency. That is, if a noun is singular, it takes a singular verb form or pronoun; if a noun is plural, it takes a plural verb form or pronoun.
Noun-verb agreement
Here are some examples of noun-verb agreement.
I am at home. ("am" agrees with the subject, "I")
She is at home. ( "is" agrees with the subject, "she")
The girls are at home. ("are" agrees with the subject, "the girls")
Pronoun-noun agreement
Pronouns take the place of nouns. If a pronoun replaces a subject, use these pronouns: I, she, he, it, they, we.
My brother and I will go to Florida in May.
If pronouns come after a preposition in a sentence, use these pronouns: me, her, him, it, them, us.
Send a reply to Sally and me.
The book belongs to him.
Here is a typical pronoun error:
Me and her went to the movies.
"Me" and "her" cannot be used as the subject of a sentence. Therefore, the correct sentence is
She and I went to the movies.
Here's another example of the same type of error:
The pizza was divided between my roommate and I.
Since the pronoun comes after the preposition "between," the sentence should read
The pizza was divided between my roommate and me.
A singular pronoun should replace a singular noun; a plural pronoun should replace a plural noun. Here, for example, is a very common pronoun mistake with a few possible revisions:
Any Â鶹Æƽâ°æ student can decorate their dorm room with posters.
This is grammatically incorrect because "Any Â鶹Æƽâ°æ student" refers to a single student, and the pronoun "their" is a plural possessive pronoun. (In the same way, "each Â鶹Æƽâ°æ student" refers to a single student, not to everyone.) There are two ways to revise such a sentence:
Any Â鶹Æƽâ°æ student can decorate his or her dorm room with posters.
Â鶹Æƽâ°æ students can decorate their rooms with posters.
If you want to avoid gender bias in choosing pronouns, changing a noun to a plural can help solve the problem. In general, overusing "his or her" construction makes writing awkward.
Click here to read more about agreement in the context of correct grammar.