Number agreement
Pronouns either replace or refer back to a noun. Accordingly, they must agree in number with the noun to which they refer or are replacing.
- Use a singular pronoun to replace a singular noun
- The cat climbed the tree but it stopped at the top branch.
("cat" is singular; "it" is also singular) - Remember that "everyone", "someone", "anyone", "each", "neither", "nobody", "someone", "a person", etc. are singular nouns; therefore, they require a singular pronoun unless a plural pronoun is being used as a gender-neutral singular pronoun
- Everyone should buy their bus pass.
("Everyone" is singular; "their" is a gender-neutral singular pronoun)
- Everyone should buy their bus pass.
- The cat climbed the tree but it stopped at the top branch.
- Use a plural pronoun to replace a plural noun
- The cats climbed the tree but they stopped at the top branch.
("cats" is plural; "they" is also plural)
- The cats climbed the tree but they stopped at the top branch.
For more information, please refer to The OWL at Purdue: Using Pronouns Clearly.