According to the Subject Verb Agreement, Subjects and verbs must AGREE with one another in number i.e.singular or plural. Therefore, if a subject is singular, its verb must also be singular and if a subject is plural, its verb must also be plural.

For example, Ram eats breakfast every morning. Here, we use "eats" because the subject (Ram) is singular. Therefore, we use the singular noun "eats" instead of "eat"