Verbs have a singular and a plural form. When using a verb in a sentence, pay attention to the subject-verb agreement. This means, that the subject and the verb must agree in number.
If a subject is singular, the verb must be singular.
If a subject is plural, the verb must be plural.
1. When you have a sentence that uses I or you as the subject, even though the subject is singular, the verb takes the plural form.
2. Another time when subjects and verbs do not have to agree is when the verbs are written in the past tense. In this case, the form of the verb is the same no matter what the subject is.
3. If there are prepositional phrases between the subject and verb, they don't affect the agreement .
4. In a sentence that starts with here or there, the subject is after the verb, so you must pay attention to make sure the two agree.
5. In questions, sometimes the subject does not always come right before the verb. So, you must pay attention to make sure the two agree.
6. When a word such as each, every, or no comes before the subject, you will always use a singular verb.
7. Two subjects joined by the word and need a plural verb.
8. Singular subjects connected by words such as or, neither/nor, or either/or have a singular verb.
9. When writing about units of measurement or time, use a singular verb.
10. Indefinite pronouns, such as somebody, everybody, everyone, and someone, use singular verbs.
Subject-Verb agreement is important because it makes a sentence easier to understand. It also helps make the sentence sound better.
Look at this sentence: "Monica play softball."
What does it mean? Is it commanding someone named Monica to play softball? No. It is a sentence where the subject and verb do not agree. The sentence should say: "Monica plays softball."
Because of this, the subject and verb must agree in number.