Parallel Structure on ACT English


Parallel structure on ACT English is a frequently referenced but often misunderstood grammar rule. The ACT commonly tests your understanding of parallel structure, usually in combination with verb-verb or noun-noun agreement.

In this article we will define parallel structure, detail the types of parallel structure questions you are likely to see on ACT English, and provide strategies that you can employ to answer parallel structure questions.

After reading this article, you will understand the concept well enough to correctly answer ACT English questions that test your knowledge of parallel structure.

What is Parallel Structure on ACT English?

Parallel structure (also called parallelism) is a repetition of the same pattern of words or phrases in a sentence. Using parallel structure shows that the words or ideas have the same level of importance and makes the sentence easier to understand.

The basic parallel structure rule is that words in a list should be in the same grammatical form. If the list contains three or more things, the construction of the list should be noun-noun-noun, or verb-verb-verb, or gerund-gerund-gerund, etc. Any inconsistency within the list is an error in parallel structure.

            Incorrect:         Mary likes hiking, swimming, and to ride a bicycle.

This sentence lists three things that Mary likes to do. The first two things are gerunds, and the third is an infinitive. In parallel structure, all three things must be in the same grammatical form.

Correct:           Mary likes hiking, swimming, and riding a bicycle.

Correct:           Mary likes to hike, to swim, and to ride a bicycle.

Both of the above versions of the same sentence are correct because items in a list match.

Parallel Structure on the ACT

The ACT English commonly tests two types of parallel structure questions.

Parallelism Type 1: Lists

The above example was a parallel structure list sentence. Usually, in list questions, three things are listed and your job is to verify that all items in the list are in the same grammatical form. Here is another “list” sentence that contains a parallel structure error:

Incorrect:         The student was asked to prepare a presentation quickly, accurately, and in a detailed manner.

Quickly and accurately are both adverbs that modify how the presentation should be prepared. However, the phrase “a detailed manner” breaks the parallel structure of this sentence. To correct this sentence, we need to replace the phrase “a detailed manner” with an adverb in the same style as the other two. Here’s a correct version of the same sentence.

Correct:           The student was asked to prepare a presentation quickly, accurately, and thoroughly.

Now all of the items are in the same form. The sentence reads better and the structure is parallel. Let’s talk about the strategy you can use to consistently answer parallel structure questions correctly.

ACT English Strategy

The first thing you must do is identify that there is a list of items. Usually, the list will be in the form of x, y, and z. Make sure the commas are separating items in a list and are not just separating clauses. Once you identify if you are dealing with a list, determine if all of the items in the list are consistent with each other.

To do that, break down each item in the list by identifying the parts of speech of the words and make sure all the items match. You are looking for an answer choice that puts all items in the list in the same grammatical form – there should be no inconsistencies. For example, after correcting the previous example, the items in the list included “quickly” (adverb), “accurately” (adverb), and “thoroughly” (adverb).

Now that you have a good understanding of how to keep parallel structure in a list, let’s talk about a more challenging type of parallel structure question.

Parallelism Type 2: Phrases

Parallel structure phrases are somewhat more complicated than the list questions, but they follow the same principle. Parallel structure phrases always involve conjunctions and the rule states that the construction of a phrase on one side of a conjunction must match the construction of a phrase on another side of a conjunction as closely as possible.

Definition of a Conjunction

Conjunctions are words that connect phrases or clauses. The most common type of conjunction is known as FANBOYS which stands for For, And, Nor, But, Or, Yet, So.

In addition, there are correlative conjunctions also known as word pairs. These words literally come in pairs. Examples of word pairs are: either … or, neither … nor, as…as, not only… but also, and both…and.

ACT English Strategy for Parallel Structure on ACT English

Let’s talk about how to apply the rules and the definition of a conjunction to parallel structure sentences.

Incorrect:         The ACT English section challenges students and frustration is found in them.

This sentence talks about two things that ACT English section does. Those two things are connected by a conjunction “and.”

If we break down each item by the parts of speech, we will notice that the first phrase “challenges students” has the construction of verb + noun, while the second phrase “frustration is found in them” has the construction of noun + verb + adjective + preposition + pronoun. Even if you are having a hard time identifying the various parts of speech, you should be able to recognize that the phrases are not consistent and that there is a parallel structure error.

ACT English Strategy (cont’d)

We can correct this parallel structure error by changing the words in the second phrase to match the verb + noun construction of the first phrase. The corrected version of this example is:

Correct:           The ACT English section challenges students and frustrates them.

The corrected phrase should read better and appear more consistent. The phrases now have the same construction and there is no parallel structure error. If you are wondering why we used a pronoun in the second phrase, remember that it is perfectly acceptable to use a pronoun in place of a noun as long as that pronoun has a clear antecedent.

In case you need more practice, here is another example.

Incorrect:         The teacher said that the student waited until the last minute to study for the exam, completed lab problems carelessly, and his motivation was low.

This is a more complicated example because it contains a list and a conjunction. It does not matter how many clauses the sentence has, all of them must follow the same construction in order to fulfill parallel structure rules.

Here, we have 3 clauses. The first two contain verbs in the past tense “waited” and “completed,” while the third has the construction of pronoun + noun + verb + adverb. To correct this sentence, all 3 clauses must have verbs that follow the same construction.

Correct:           The teacher said that the student waited until the last minute to study for the exam, completed lab problems carelessly, and lacked motivation.

Now the sentence is consistent, there is clear verb-verb-verb agreement and there is no parallel structure error.

ACT Example

Let’s consider how ACT English section tests the concept of parallelism.



This is a parallel structure error question. This sentence describes the results of an experiment that “revealed” that snowflakes do two things. They are connected by a conjunction “and.”

The first thing snowflakes do is “begin” a chemical process. The subject of this sentence is “snowflakes” which is a plural noun. According to subject-verb agreement rules, a plural noun must be paired with a verb in the plural form. The word “begin” fulfills that requirement. In order to satisfy the rules of parallel structure, the second thing snowflakes do must be described by a plural verb. We can eliminate choice F because “forms” is a singular verb. G and H can be eliminated because they are too wordy and create confusion in the sentence. We are left with option J which is the correct answer – the verb “form” is plural and follows parallel structure where “begin” and “form” are consistent.

Summary: Strategies for Answering Parallel Structure on ACT English Questions

#1. Any Word or Phrase Underlined Within a List Signals a Possible Error in Parallel Structure.

Whenever you see a list of words, phrases, or clauses make sure that all items are in the same grammatical form.

#2. Phrases that Appear Before and After a Conjunction Must Be Parallel

The parallel structure within “phrases” is more complex than parallel structure within “words.” Be on a lookout for common conjunctions and correlative conjunctions such as and, but, not only… but also, so…that, at once … and, both … and, either … or, as … as.

In order to identify parallel structure within phrases easier, make sure you are reading the entire sentence and determining parallelism within the context, not just by looking at the underlined portion.

#3. Break Down Construction of Items Within a List

Identify parts of speech within words or phrases before and after a conjunction. Constructions of all items must match each other as closely as possible.

Next Steps

Congratulations on putting in effort to improve your ACT score. Your time and effort investment should pay off.  As you continue studying for the ACT English section, make sure you consider the article on 5 critical concepts you must know for ACT English. Also, because punctuation is such a frequently tested topic, I encourage you to read our articles about commas on the ACT.

If you are wondering which test is better for you, read this article detailing the differences between SAT vs. ACT (coming soon).

To watch a YouTube video with the information included in this blog post, please follow this link.

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