Below you’ll find a comprehensive explanation of subject/verb agreement taken from GALILEO, University System of Georgia GALILEO Open Learning Materials. You’ll want to review the material carefully! If you’re more of a visual person, you might find this youtube tutorial equally as useful: 

Subject-Verb Agreement

Subject-verb agreement is one of the most common errors that people make. Having a solid understanding of this concept is critical when making a good impression, and it will help ensure that your ideas are communicated clearly.

Basic Agreement

Agreement in speech and in writing refers to the proper grammatical match between words and phrases. Parts of sentences must agree, or correspond with other parts, in number, person, case, and gender.

1. Number. All parts must match in singular or plural forms.

2. Person. All parts must match in first person (I), second person (you), or third person (he, she, it, they) forms.

3. Case. All parts must match in subjective (I, you, he, she, it, they, we), objective (me, her, him, them, us), or possessive (my, mine, your, yours, his, her, hers, their, theirs, our, ours) forms.

4. Gender. All parts must match in male or female forms.
Subject-verb agreement describes the proper match between subjects and verbs.

Because subjects and verbs are either singular or plural, the subject of a sentence and the verb of a sentence must agree with each other in number. That is, a singular subject belongs with a singular verb form, and a plural subject belongs with a plural verb form.

Regular Verbs

Regular verbs follow a predictable pattern. For example, in the third person singular, regular verbs always end in -s. Other forms of regular verbs do not end in –s.

Tip

Add an -es to the third person singular form of regular verbs that end in -sh,-x, -ch, and -s. (I wish/He wishes, I fix/She fixes, I watch/It watches, I kiss/He kisses.) In the singular form, the pronoun you refers to one person. In the plural form, the pronoun you refers to a group of people, such as a team. Many singular subjects can be made plural by adding an -s. Most regular verbs in the present tense end with an -s in the third person singular. This does not make the verbs plural.

Irregular Verbs

Not all verbs follow a predictable pattern. These verbs are called irregular verbs. Some of the most common irregular verbs are be, have, and do. Learn the forms of these verbs in the present tense to avoid errors in subject-verb agreement.

Be

Have

Do

Errors in Subject-Verb Agreement

Errors in subject-verb agreement may occur when

•   a sentence contains a compound subject;
•   the subject of the sentence is separate from the verb;
•   the subject of the sentence is an indefinite pronoun, such as anyone or everyone;
•   the subject of the sentence is a collective noun, such as team or organization;
•   the subject appears after the verb.

  Recognizing the sources of common errors in subject-verb agreement will help you avoid these errors in your writing. This section covers the subject-verb agreement errors in more detail.

  Compound Subjects

  A compound subject is formed by two or more nouns and the coordinating conjunctions and, or, or nor. A compound subject can be made of singular subjects, plural subjects, or a combination of singular and plural subjects.

  •   Compound subjects combined with and take a plural verb form.
  •   Compound subjects combined with or and nor are treated separately. The verb

    must agree with the subject that is nearest to the verb.

    Tip

    If you can substitute the word “they” for the compound subject, then the sentence takes the third person plural verb form.

Intervening Phrases or Clauses

As you read or write, you may come across a sentence that contains a phrase or clause that separates the subject from the verb. Often, prepositional phrases or dependent clauses add more information to the sentence and appear between the subject and the verb. However, the subject and the verb must still agree.

If you have trouble finding the subject and verb, cross out or ignore the phrases and clauses that begin with prepositions or dependent words. The subject of a sentence will never be in a prepositional phrase or dependent clause.

Indefinite Pronouns

When an indefinite pronoun serves as the subject of a sentence, you will often use a singular verb form. However, keep in mind that exceptions arise. Some indefinite pronouns may require a plural verb form. To determine whether to use a singular or plural verb with an indefinite pronoun, consider the noun that the pronoun would refer to. If the noun is plural, then use a plural verb with the indefinite pronoun.

Collective Nouns

Because collective nouns are counted as one, they are singular and require a singular verb.

Example: The class respects the teacher.

The Subject Follows the Verb

You may encounter sentences in which the subject comes after the verb instead of before the verb. To ensure proper subject-verb agreement, you must correctly identify the subject and the verb.

Example: Somewhere deep in the woods reigns the king of the elves. In this example the verb (reigns) comes before the singular subject (king).

Here or There

In sentences that begin with here or there, the subject follows the verb. If you have trouble identifying the subject and the verb in sentences that start with here or there, it may help to reverse the order of the sentence so the subject comes first.

Example: There were many athletes training in the gym.

In this example the verb is were and the subject is athletes. (Note: training is not the verb of this sentence. training in the gym is a participial phrase. See Components of a Sentence.)

Questions

Many questions are formed with helping verbs whose form must agree in number with the subject:

Example: Are you going to the party tonight? Answer: Yes, I am going to the party.

The verb tense used in the question is present progressive (are going), and the subject (you) is placed after the helping verb are but before the present participle going.

Example: Does your car run? Answer: Yes, my car runs.

In this example, notice that the s ending for the singular subject (car) appears at the end of the helping verb does in the question. In the answer to the question, the s ending is attached to the verb run, and the helping verb is not used.

Tip

If you have trouble finding the subject and the verb in questions, try answering the question being asked.