Subject-verb agreement is a grammatical rule in English that ensures the subject and verb in a sentence are in harmony with each other in terms of number and person. This means that the form of the verb must match the subject in number (singular or plural) and sometimes in person (first, second, or third person). Here’s a breakdown:

Singular and Plural Agreement:

Singular Subject: Use a singular verb form.

Example: She walks to the park.

Plural Subject: Use a plural verb form.

Example: They walk to the park.

Third-Person Singular:

In the present tense, third-person singular subjects (he, she, it) require an -s or -es ending on the verb.

Example: He runs every morning.

Collective Nouns:

Collective nouns (e.g., team, group, family) can take either singular or plural verbs depending on whether the noun is being considered as a single unit or as individual members.

Example (singular): The team is winning.

Example (plural): The team are arguing among themselves.

Indefinite Pronouns:

Indefinite pronouns like everyone, somebody, and each are typically treated as singular.

Example: Everyone is invited to the party.

Compound Subjects:

When a subject is made up of two or more nouns joined by and, the verb is usually plural.

Example: The cat and the dog are playing.

When the subjects are joined by or or nor, the verb should agree with the subject closest to it.

Example: Either the teacher or the students have left.

Exceptions and Irregularities:

Some cases, such as with none or either/or, can be trickier and may require context to determine the correct verb form.

Proper subject-verb agreement ensures clarity and correctness in writing and speaking, making it easier for the reader or listener to understand the intended meaning.