Noun-pronoun disagreement is one of the most common errors in written and spoken American English. It appears most often when people want to use the gender-neutral "they" or "their" in lieu of the awkward "he or she" or "his or hers."
To avoid this error, the writer needs to identify the noun that a pronoun refers to, determine whether it is singular or plural, and use the appropriate singular or plural pronoun.
Here are some examples, with the nouns and pronouns underlined:
WRONG: The team was pleased with their score.
CORRECT: The team was pleased with its score.
CORRECT: The players were pleased with their score.
WRONG: Any student who wants to join should send their contact information to the club secretary.
CORRECT: Any student who wants to join should send his or her contact information to the club secretary.
CORRECT: Students who want to join should send their contact information to the club secretary.
Note that the answer does not always lie in changing a plural pronoun to a singular one; it is often easier and less awkward to convert a singular noun to a plural one.
© Holly A. Heyser