What does it mean when a pronoun must agree in number with the noun it replaces?

When a pronoun must agree in number with the noun it replaces, it means that the pronoun should mirror the number of the noun. In the context of this particular statement, if a noun is singular, then the pronoun must also be singular. This ensures clarity and precision in language. For example, if the noun is "dog," which is singular, the appropriate pronoun would be "he," "she," or "it," rather than "they," which is plural. This agreement helps to avoid confusion about which noun the pronoun refers to, maintaining coherence in communication.

The concept of pronoun-noun agreement is fundamental in constructing grammatically correct sentences, making it essential for clear writing and effective communication.