In every child's education comes the moment when verbs are defined as action words. That is a fairly easy concept to master, but use of singular versus plural verbs and correct subject-verb agreement are more abstract concepts and require more detailed explanations. Correct use of singular and plural verbs also depends on the writer's ability to correctly identify the subject of the sentence and to determine if the subject is singular or plural.
Base words are the basic form of any word. The base form of a verb is the form from which singular and plural forms of the verb are derived. The base form of any verb can be changed into a singular or plural, past tense, present tense or future tense verb by adding different endings such as -ed, -s, -es and -ing. Some examples of base verbs are smile, confess and laugh. All of these can be changed by adding different endings or in the case of irregular verbs, different spellings or a different word altogether. Most regular verbs are changed from singular to plural verbs by simply adding -s or -es to the end of the base word.
To master subject-verb agreement, you must be able to provide singular verbs for singular subjects and plural verbs for plural subjects. Sentences with singular subjects written in the present tense will have a verb that ends in -s or -es. Sentences that are present tense with plural subjects will have verbs that do not end in -s or -es unless the base word usually ends in s. Some examples are "The dog runs," which has a singular subject and singular verb ending in -s, and "The brothers smile," which has a plural subject and plural verb not ending with -s. Even irregular verbs with different words for singular and plural will follow the rule that singular verbs end with -s. For instance, "Jake is" has a singular subject and singular verb ending in -s. "The clowns are" has a plural subject and plural verb not ending in -s.
Singular or Plural
When a verb is regular and ends with -s or -es, it is considered a present tense, singular verb and should be used with a singular subject. Sentences that have singular subjects and singular verbs are: "The boy smiles." or "The man confesses." Adding -s or -es is determined by spelling rules concerning words ending with s, ss or x. For instance, the word confess becomes a singular verb by adding -es because the base word ends with s. The plural form of every regular verb will be the base word and will not end with -s or -es unless the spelling of the base word usually ends with s.
The -s and -es rule is only true for present tense verbs. Verbs that are past tense will not change form to indicate singular or plural verbs. Most verbs are made past tense by adding -ed. Some irregular verbs have a different spelling for past tense such as the word run, which becomes ran in past tense. When a verb is past tense, the spelling will be the same whether the verb is singular or plural. The writer would not add -s or -es. To say "the boys jumped" or "the boy jumped" is correct although one has a singular subject and one has a plural subject.
Future tense verbs are usually preceded by the word will to indicate that the action has not taken place yet. Again, as with past tense verbs, the verb will not change from a singular to a plural but will remain the same: "The boys will jump." or "The boy will jump."
The most common error when deciding to use singular or plural nouns comes with a sentence subject that is not immediately followed by the verb as in more complex sentences. For instance, the first sentence in this section is a complex sentence. The subject of this sentence, "error," is singular, but the plural, "nouns," appears just before the verb. Some writers find this confusing and will use the word closest to the verb to determine whether the verb should be singular or plural. Another example of a complex sentence is: "The crowd, which is made up of many citizens, protests the rule." In this sentence about the crowd of citizens in which the word citizens is plural, the verb, "protests," is singular ending in -s, because the subject of the sentence, "crowd," is singular. There is only one crowd. As sentences become more complex, correct subject-verb agreement becomes more difficult for the writer.