Verb agreement is a matching relation between subject and verb, the main rule of agreement is: singular subjects go with singular verb phrases plural subjects go with plural verb phrases. In present...
Basic Principle: Singular subjects need singular verbs; plural subjects need plural verbs. My brother is a nutritionist. My sisters are mathematicians.
See the section on Plurals for additional help...
In the present tense third person: if the noun is singular the verb must have an -s eg He likes ice cream. The dog eats ice cream. if the noun is plural the verb does not have an -s eg They like ice...