Subject-verb agreement means the verb in a sentence must match its subject in number. A singular subject takes a singular verb; a plural subject takes a plural verb.
This rule applies every time you build a sentence in English. Most of the work happens in the present tense, where the verb changes its form depending on who or what the subject is.
The core rule: present simple
In the present simple, a third-person singular subject (he, she, it, or any single person or thing) takes a verb with -s or -es. All other subjects use the base form of the verb.
| SUBJECT | VERB FORM | EXAMPLE |
|---|---|---|
| I | base | I speak French. |
| you | base | You drive too fast. |
| he / she / it | base + -s | She speaks French. |
| we | base | We drive to work. |
| they | base | They speak Italian. |
The -s ending is the single biggest signal of agreement in English. Forgetting it or adding it to the wrong subject is one of the most common errors at every level.
Spelling: -s, -es, -ies
Most verbs simply add -s: plays, reads, costs, helps.
Verbs ending in -ch, -sh, -ss, -x, -o add -es: watches, finishes, passes, fixes, goes.
Verbs ending in a consonant + y change y to -ies: studies, carries, flies. But if a vowel comes before y, just add -s: plays, stays, enjoys.
The verb *be*
The verb be is the only English verb that changes form for more than just third-person singular. It has three present forms and two past forms.
Present
| SUBJECT | FORM |
|---|---|
| I | am |
| you / we / they | are |
| he / she / it | is |
Past
| SUBJECT | FORM |
|---|---|
| I / he / she / it | was |
| you / we / they | were |
No other English verb behaves this way. Regular verbs in the past tense use one form for every subject: I worked, she worked, they worked.
Finding the true subject
The subject is the word that answers the question "who or what does the action?" Once you find it, make the verb agree with that word alone.
This sounds straightforward, but real sentences often place extra words between the subject and the verb. Those words do not change agreement.
Prepositional phrases
A phrase starting with of, in, with, on, for, between, among or similar prepositions is never the subject.
The subject is price (singular), not tickets. The phrase of the tickets only describes which price.
The subject is box, not chocolates.
Here, results (plural) is the subject, so the verb is plural.
Relative clauses and other modifiers
Sometimes an entire clause sits between the subject and the verb. Ignore it for agreement purposes and match the verb to the main subject.
The subject is students (plural). The clause who passed the exam is a modifier.
The subject is manager (singular), even though three departments appears nearby.
The subject is report (singular). Everything between report and needs is a modifier.
A note on *I*
The pronoun I is always singular, yet it uses the base form of the verb, not the -s form: I work, I drive, I know.
This puts I in the same column as plural subjects grammatically, even though it refers to one person. It is simply a feature of English: I has its own agreement pattern, and the key point is that it never takes -s.
With be, I has a unique form in the present (I am) and shares a form with singular subjects in the past (I was).
Common mistakes
Missing -s with he / she / it
Adding -s with plural or other subjects
Wrong form of be
Tricked by words between subject and verb
Ignoring the main subject in longer sentences