The concept of subject and verb agreement is based on the number of the subject. While writing English sentences, one should be aware of correctly identifying whether the subject is singular or plural and accordingly use the verb. Basically a singular subject takes a singular verb and a plural subject takes a plural verb. For example, in the sentence: She writes books, the subject, ‘she’ is singular and so the singular verb, ‘writes’ is used. If two subjects are connected by ‘and’ there should be a plural verb. However, if two subjects are connected by ‘or’ or ‘nor’ singular verbs should be used. At the same time, the pronouns, everyone, anyone, each and someone are considered singular and these require singular verbs. Besides, when one expresses quantity of time, money and distances, only singular verbs are used.
For example: Ten dollars is a lot of money for this product.
It is good to remember that collective nouns like team, staff, and committee are singular subjects and require singular verbs in any context. These are only the main features of subject-verb agreement.