Recognize subject–verb agreement errors

Every language has rules that help people understand each other. In English, one of the oldest and most important rules is subject–verb agreement. This rule says that the subject of a sentence and its verb must match in number. If the subject is singular (one thing), the verb must be singular too. If the subject is plural (more than one), the verb must be plural.

This rule has been part of English grammar for hundreds of years. As people wrote dictionaries, textbooks, and grammar guides, they carefully described how subjects and verbs work together. Let's look at a few key moments in the history of English grammar.

So here's the big question this lesson answers: How do you spot a subject–verb agreement error, especially when the sentence tries to trick you?

Before you can find errors, you need to understand the basic rules. Subject–verb agreement comes down to one idea: a singular subject takes a singular verb, and a plural subject takes a plural verb. Here are the key principles you need to know.

The diagram below shows how to match subjects and verbs. On the left side, you'll see singular subjects with their correct singular verbs. On the right, you'll see plural subjects with their correct plural verbs. The red X marks show what happens when you mismatch them.

Notice a tricky pattern: for most nouns, you add -s to make them plural (dog → dogs). But for most verbs, you add -s to make them singular (run → runs). This opposite pattern is one reason agreement errors are so common.

The biggest trick on the TACHS is when extra words sit between the subject and the verb. These interrupting phrases (also called prepositional phrases) can make you think the wrong word is the subject. Your job is to mentally cross out those extra words and find the true subject.

The "Cross-Out" Strategy

Here's a simple three-step strategy. First, find the verb. Second, ask "Who or what does this action?" Third, cross out any phrase that begins with words like of, with, along with, together with, as well as, in, on, at, or including. Those phrases are just extra information — they don't change the subject.

Special Cases with "Be" Verbs

On the TACHS, the easiest errors are the ones no one misses. The test makers know this, so they set clever traps. Let's look at the five trickiest patterns so you can spot them right away.

Indefinite Pronouns — A Closer Look

For the "singular or plural" column, look at what the pronoun refers to. "Some of the cake is gone" (cake is singular). "Some of the cookies are gone" (cookies is plural).

Let's walk through a TACHS-style question together. Read the sentence below and try to find the error before looking at the steps.

Here are the most common errors students make on the TACHS. Study the "Wrong" column and notice how each one breaks the agreement rule. Then look at the "Why" column to understand the fix.

Once you master basic subject–verb agreement, you'll be ready for harder grammar skills in high school and beyond. Here's how the concept grows as you advance.

On the TACHS, you only need to identify errors — you don't need to fix them. But learning to fix them now will make you a stronger writer and reader. Every time you catch an error, you're building a skill that will help you in high school English class, college essays, and even professional writing.

Try these five problems on your own. For each sentence, decide if there is a subject–verb agreement error. If there is, explain what the error is and how to fix it. The problems get harder as you go!