Page 621 - Wordsmith A Guide to College Writing

person plural and require a present-tense plural verb, the form that
does not add s or es.

The Verb to be

Now look at the most common irregular verb, the verb to be.

Singular Plural

First person I am we are

Second person you are you are

Third person he, she, it is they are

Notice that the pattern still holds: The third-person singular form of the

verb always ends in s or es.

A Fundamental Rule

Knowing the pattern that present-tense verbs follow should make it a

bit easier to apply the fundamental rule of subject-verb agreement:

A singular subject requires a singular verb, and a plural subject

requires a plural verb.