Much of the ACT English section asks you to tell the difference between a complete sentence and a fragment. To do that, you need to coordinate several skills, including correct use of commas, semicolons, colons, clauses, and more.

A complete sentence needs two things:

1. A subject-verb set
2. A complete sentence expression

A subject-verb set means you have a main noun (the subject) and an action or state of being (the verb) that goes with that subject. They work as a pair. As discussed elsewhere, they’re also defined by each other in important ways.

The dog wondered about its future, looking at the vet clinic.

Start by finding the verb. You might first notice looking, since it clearly shows action. So ask:

“Does something in the sentence ‘look’? Does the sentence say the dog looked?”

Not exactly. “Dog looking” doesn’t work as the main subject-verb set here, so looking probably isn’t the main verb. Instead, ask: the dog did what?

The dog wondered. That’s the main action. Now you have the correct subject-verb set: dog-wondered.

Next, check whether the sentence expresses a complete thought. It does: you know the dog wondered, what it wondered about, and the context. So this is a complete sentence.

Let’s look at another.

Which he didn’t fully understand.

Understand looks like an action. Did someone “understand”? Yes - he did. And since did is a helping verb, the full subject-verb set is he did understand.

Now check for a complete thought: Which he didn’t fully understand. The word which prevents this from being a complete thought. It signals that the sentence is referring back to something earlier - but here, you don’t know what. Which must refer to a specific noun or idea, and this sentence doesn’t provide it.

Look at the following examples. Each one includes a word or structure that prevents it from expressing a complete thought.

• After he had gone to the store for milk
• Because what her boss told her was obviously incorrect
• That they looked forward to the evening.

Other fragments happen because they don’t have a proper subject-verb set. These are phrases, not full clauses or sentences:

• Working tirelessly every single day
• Another example of the statistic
• To win the day despite the challenge

Look at the first bullet point above.

Working looks like a verb, but there’s no subject - nothing that actually does the working. So there’s no subject-verb set.

Example

Now, let’s look at an example of this as it will appear on the ACT.

Scientists analyzed the patterns revealed by the study since it would apply to other situations.

A. NO CHANGE
B. study, since
C. study; since
D. study. Since

Take a stab at it and see if you can answer the question correctly.

Do you know the answer:

Whether you answered the question correctly or not, keep reading. It’s important to understand exactly why each wrong answer is incorrect and why only one is correct.

This looks like a punctuation question, and it is. But underneath the punctuation, the real issue is fragments versus complete sentences.

Option D shows this clearly. If you put a period there, you create two separate sentences:

• The first clause, “Scientists analyzed the patterns revealed by the study,” works as a complete sentence. It has a subject-verb set (scientists-analyzed) and expresses a complete thought.
• The second clause, “since it would apply to other situations,” has a subject-verb set (it-would apply), but it does not express a complete thought. Starting with since makes it dependent: it needs to be attached to an independent clause (a complete sentence) to be complete.

Choice C can be tempting if you forget that semicolons can only link independent clauses (complete sentences). Since what comes after the semicolon isn’t a complete sentence, the semicolon doesn’t work.

Choice B adds a comma, but no comma is needed here. When you have an independent clause followed by a dependent clause, you generally use a comma only if the dependent clause comes first. See the chapter Linking dependent clauses.

Choice A is the correct answer.

Preparing for sentence fragment questions on the ACT

The test quizzes you on sentence fragments frequently, so we added a few more questions than usual. Make sure you drill these questions so you can recognize fragments quickly on test day.