A subject is a noun, pronoun, or noun phrase that is the focus of a clause. If the clause contains a verb, the subject is the agent that performs the verb action.
A verb is a word that indicates action or a state of being,. It describes what the subjects are, or are doing. In English, verbs change form — to either singular or plural — to agree with the number of their subjects (i.e., one, or more than one). Only verbs that are in present tense need to change form.
The best way to learn subject-verb agreement is to see how it is applied in a variety of situations. Consider the following sentence:
The door are unlocked.
The verb (are) is in the plural form, but the subject (door) is singular. Correction of the verb form, so that it agrees with the subject, produces the following result:
The door is unlocked.
The subject and verb now agree: The singular subject (door) is followed by a verb in singular form (Is).
Here's another example:
One of the doors are unlocked.
Does this sentence sound correct? To determine whether it is (or is not), first identify the subject. In this sentence, the subject is found in the opening phrase: "One of the doors." The subject is "one," which is singular. The verb, therefore, should also be singular, as in the following revision:
One of the doors is unlocked.
Sometimes verb form does not agree with a plural subject, as in this example:
Both doors is unlocked.
Here's the correct way to write this sentence:
Both doors are unlocked.
Subject-verb agreement is not always as easy to detect and correct as it was in the preceding examples. Sometimes sentence structure can lead even experienced writers to make mistakes. Some are easier to identify — and fix — than others.
The following sentence contains two subjects that are joined by "and:"
Marie and John is running away.
How should this sentence be corrected? The verb must be plural, since the sentence has two subjects, Marie and John:
Marie and John are running away.
Here's another example using two subjects:
The dog and the cat plays outside.
This one can be corrected in the same way as the previous example. The verb must be rewritten in plural form, since there are two subjects:
The dog and the cat play outside.
The following example is similar to the last, but different in a significant way:
Either Marie or John are running away.
In this sentence the word that connects the nouns (i.e., Marie, John) is "or," not "and." When "or" is used, each of the connected nouns is treated as a singular subject (i.e., there's only one subject, either Marie or John). Therefore, the verb should be in singular form:
Either Marie or John is running away.
Here is another example in which "or" is used:
The nut or bolt need replacing.
The rule regarding "or" that was applied in the preceding example applies here as well. Here's the corrected version. The verb has been changed to singular form:
The nut or bolt needs replacing.
Another special situation involves "group subjects," as in the following sentence:
The family enter the restaurant.
Even though "the family" no doubt includes more than one member, the collective noun ("family") that is the subject of this sentence, is singular. The verb, therefore, should be in singular form:
The family enters the restaurant.
Do the subject and verb of the following sentence agree?
One of the teams are cheating.
As written, this sentence is incorrect. The subject is found in the opening phrase: "One of the teams." The subject of this sentence is "one," which is singular:
One of the teams is cheating.
This may sound incorrect because of the proximity of "teams" (plural) to the verb (is). Remember that "teams" is not the subject of the sentence: The subject of this sentence is "one," which is singular. The verb, therefore, must be in singular form (is).
The following sentence is an example of another special situation:
The little boy, along with his parents, play in the yard.
This sentence may seem correct at first glance, because the subject and verb are separated by this clause: "along with his parents." The subject (boy) is singular, so the verb must be written in singular form:
The boy, along with his parents, plays in the yard.
Here's another example in which separation of subject and verb can lead to an error in agreement:
The old woman with 20 cats live in that house.
The subject of this sentence (i.e., woman) is singular. The verb, therefore, must be written in singular form:
The old woman with 20 cats lives in that house.
The use of pronouns can also lead to problems in subject-verb agreement, as in this sentence:
Everyone love Popsicles.
The pronoun that is the subject of this sentence (everyone) may seem to be plural., but it is not. Although it is written as one word (everyone), its meaning is every one — and one is singular. Here's the corrected sentence, in which subject and verb agree:
Everyone loves Popsicles.
Here's another example:
Many disagrees with me about dinner etiquette.
The pronoun that is the subject of this sentence (many) is plural. The verb form must match it:
Many disagree with me about dinner etiquette.
The following sentences contain one subject that is singular, and another that is plural:
The cat and the dogs is hungry.
The subjects are cat (singular) and dogs (plural). The sentence should be corrected as follows:
The cat and the dogs are hungry.
That's right, but suppose the sentence had been written this way:
The dogs and the cat is hungry.
That almost sounds correct, doesn't it? However, verb form is not determined by the order in which subjects are presented, or the proximity of a particular subject to the verb. Remember that when there are multiple subjects, the verb must be plural:
The dogs and the cat are hungry.
Source: Adapted from Sophia Instructor Gavin McCall