The basic idea behind subject-verb agreement is pretty simple: all the parts of your sentence should match (or agree). Verbs should agree with their subjects in number (singular or plural) and in person (first, second, or third). In order to check agreement, find the verb and ask who or what is doing the action of that verb. This is another of those grammatical concepts that sound like something you could never get wrong… but we just got it wrong in that sentence. It should read, “this … sounds like,” not, “this … sound like.” The verb “to sound” modifies “this,” not “grammatical concepts.” Incorrect subject-verb agreement is not an error you’re likely to make when you’re comfortable with the subject matter you’re writing about, but as written assignments across the general education curriculum push you out of your comfort zone (which happens to everyone), this grammatical point is one where the stress seems to show.

Person

Agreement based on grammatical person (first, second, or third person) is found mostly between verb and subject. For example, you can say “I am” or “he is,” but not “I is” or “he am.” This is because English grammar requires that the verb and its subject agree in person. The pronouns I and he are first and third person respectively, as are the verb forms am and is. The verb form must be selected so that it has the same person as the subject.

Number

Agreement based on grammatical number can occur between verb and subject, as in the case of grammatical person discussed above. In fact, the two categories are often conflated within verb conjugation patterns: there are specific verb forms for first person singular, second person plural and so on. Some examples:

• I really am (1st pers. singular) vs. We really are (1st pers. plural)
• The experiment succeeds (3rd pers. singular) vs. The experiments succeed (3rd pers. plural)

More Examples

Compound subjects are joined by a coordinating conjunction (and, or, neither, nor). They are plural because there are more than one of them, and, typically, their verbs should be plural, too. Look at the following sentence for an example:

• A pencil, a protractor, and a calculator are necessary for the assignment.

Using the principle that “in order to check agreement, find the verb and ask who or what is doing the action of that verb,” you would ask here, “What is necessary?” The answer is, “A pencil, a protractor, and a calculator,” which are three things, so the concept is plural and requires are, not is, for agreement. If we only needed a calculator, we would write, “A calculator is necessary for the assignment.” A subject isn’t compound just because it is plural: “Calculators are necessary” is a plural subject that takes a plural verb, but it isn’t a compound subject because calculators are the only thing you need.

And, just to nuance this discussion a little more, some compound subjects actually take a singular verb because they form a singular concept. You might say, for example, “Spaghetti and meatballs is delicious” because “spaghetti and meatballs” functions as one concept (the meal). You can say, “Spaghetti and meatballs are delicious,” but that means that you are considering spaghetti and meatballs as two different entities, not as a meal. Meatballs and ice cream are delicious, but meatballs and ice cream is not.

Verbs do not agree with nouns that are in prepositional phrases. To make verbs agree with their subjects, follow this example:

• The performance of the three plays is the topic of my talk.

The subject of “my talk” is performance, not plays, so the verb should be singular. Using the principle that “in order to check agreement, find the verb and ask who or what is doing the action of that verb,” you would ask here, “What is the topic?” The answer is, “The performance.” “The three plays” are nouns in a prepositional phrase because they follow the preposition “of.”

In the English language, verbs usually follow subjects. But when this order is reversed, the writer must make the verb agree with the subject, not with a noun that happens to precede it. For example:

• Beside the house stand sheds filled with tools.

The subject is sheds; it is plural, so the verb must be stand. Using the principle that “in order to check agreement,  find the verb and ask who or what is doing the action of that verb,” you would ask here, “What stands?” The answer is “Sheds stand,” not “The house stands.”

Here’s a grey area: do we use a singular or plural verb when agreeing with a noun that is singular in grammar but plural in meaning? For example, do we say, “The faculty meets” or “The faculty meet”? Other examples include team, committee, administration, press, class, staff, and audience. Generally, in American standardized English (but not in British standardized English), these collective nouns agree with singular verbs: “The faculty meets,” “The audience applauds,” “The legal team investigates,” “The administration obfuscates.” However, when members of the collective group are acting individually, the noun and its agreeing verb are often treated as plural: “The Geology faculty are going on various field trips with their students this week.”

Agreement

All regular verbs (and nearly all irregular ones) in English agree in the third-person singular of the present indicative by adding a suffix of either -s or -es.

Look at the present tense of to love, for example:

The highly irregular verb to be is the only verb with more agreement than this in the present tense: