Subject-verb disagreement, where the conjugation of the verb does not match the point of view (first, second, or third) and number (singular or plural) of the subject, is a common error in writing.
A single relationship lies at the heart of every sentence in the English language. Like an indivisible nucleus at the center of an atom, the subject-verb pair unifies the sentence. It can be surrounded by any number of modifying words, taking on new shades of meaning, but no matter how many adjectives, adverbs, and independent clauses become attached, the basic unit remains. The subject-verb pair guarantees that the sentence means something. Without this core, a sentence fragments and loses its power to speak. Indeed, a sentence only becomes complete when it contains at least a subject and a verb.
A verb denotes action, existence, or occurrence. A subject denotes the person or thing that performs the action, the person or thing that exists, or the incident that occurs. For example:
In English, subjects and verbs must also agree with one another. That is, the form of the verb has to match the number of things in the subject. A singular subject takes a singular verb, while a plural subject takes a plural verb. For example:
Notice that, unlike nouns, regular verbs in the present tense become plural by subtracting the letter s from the end. In the past tense, verbs usually don't change at all:
No matter what kind of verb you're using, the trick to making your subjects and verbs agree with one another is to first identify the quantity of the subject and then use the appropriate verb form. Usually, the writer makes these calculations without effort. However, certain words and phrases defy such common sense evaluations. The following sections explore the most frequent areas of confusion.
The indefinite pronouns anyone, everyone, someone, no one, everybody, and nobody are always singular, and require singular verbs.
It is tempting to think that a word like everybody is plural (after all, it seems to refer to a group of people). But everybody is a shorthand way of saying "each person in the group", and therefore remains a singular word.
Some indefinite pronouns, such as some or all, can be either singular or plural, depending on the quantity of the things they refer to. For example, particulate things, like marbles or slices of bread, are countable, and therefore take plural verbs:
Non-particulate things, such as loyalty or air, are not countable, and therefore take singular verbs:
Many nouns masquerade as plural nouns, but like some indefinite pronouns, actually count as singular nouns. Words such as audience, dozen, jury, group, and team imply a plurality of members, but when those members act as one, the noun is singular, and takes a singular verb.
However, if the members of the collective noun are not acting as a group, then the noun becomes plural and takes a plural verb.
Note that a collective noun also becomes plural when more than one of the same kind of group described by the noun appears in the sentence.
When you are in doubt about whether a collective noun is plural or singular in your sentence, you can do one of two things:
Nouns that express amounts of concepts like time, money, and distance are singular.
Fractions are singular if they modify singular nouns and plural if they modify plural nouns.
Certain phrases, such as along with, including, as well as, and together with do not operate on the subject in the same way that the word and does. The word and, used to connect two nouns or pronouns, compounds them into a plural subject. But the phrases listed above only interrupt the link between subject and verb, leaving the subject's quantity unchanged:
When these pronouns appear by themselves, they are singular, even though their use connects two things:
However, when they appear with the conjoining words nor (for neither) and or (for either), the quantity of the subject closest to the verb determines the quantity of the verb:
(Note that the last sentence sounds a little strange. While grammatically correct, the move from plural to singular in the subject feels awkward. When faced with a situation like this, simply switch the order of the terms so that the plural element of the subject appears closest to the verb, and use the plural form of the verb.)
In the same way, phrases that come between the subject and the verb (usually set off with commas, parentheses, or dashes) do not contribute to the quantity of the verb:
Even though these words often appear at the beginning of a sentence (the traditional position for subjects), when they do so, they do not necessarily operate as a subject. In cases where here and there function in tandem with the verb to be (or one of its conjugates), they are part of the verb phrase rather than part of the subject:
In these cases, the subject of the sentence follows the verb, but still determines the quantity of the verb.
The rules listed above by no means exhaust every possible problem you'll encounter when paring subjects with verbs. They address only the most common areas of confusion. If, after consulting this article, you don't find a solution to the issue your sentence is facing, you could do some additional research, consulting websites or grammar/style textbooks. But you might also consider re-composing the sentence according to a different pattern.
Often, developing writers try to make their sentences do too much work, a tendency that can cause problems with subject-verb agreement. Before going through a lengthy research process, ask yourself if the sentence in question might be written in a more straightforward manner. In academic writing, your ideas should be complex. Your sentences, however, don't necessarily have to be. The strongest sentences are often the simplest.
Source: Brogan Sullivan, https://writingcommons.org/subject-verb-agreement
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