20 ACT Grammar Rules 

If you want to excel on the ACT, you’ll have to really know your grammar. As you get ready to take the ACT, you might be wondering just how many questions will actually be about grammar. Expect to see more than half of the exam testing your grammar skills as every ACT English section will have a variety of grammatical questions. The more you familiarize yourself with ACT grammar tips and understand the different ACT grammar rules, the more you’ll set yourself up for success on the ACT.

But we understand! It can feel like a colossal wave figuring out where to even begin your ACT grammar preparation. Though we won’t dive into every meticulous rule of law in the English language here, you’ll find below the most tested 20 ACT grammar rules to help you on the day of the exam. Oftentimes, students will see that the ACT grammar rules cover concepts that they had already known very well, but just hadn’t categorized.

Before we dive in, it’s great to familiarize yourself with the layout of the exam. The ACT English exam lasts for 45 minutes and consists of 75 multiple-choice questions, which are then divided into 5 essays with 15 questions each. You’ll be tasked to read these essays, and as you do, one helpful tip is to read them as though you are the peer reviewer. Take a look at every word, sentence, and paragraph, and determine which of the following grammar rules they are adhering to – or not. And if you find any sentence not flowing well, you can be sure that the grammar is off.

1) ACT Grammar Rule: There is a subject and a predicate in every complete sentence

Be sure to identify the subject, predicate or fragment. Remember, the subject is who or what the sentence is all about – the focus. The predicate is the part of the sentence that holds the verb – it finishes the action of the sentence.

For example, let’s look at the sentence: “Julian loves the beach.” Can you spot the subject (Julian) and the predicate (loves the beach)? If the sentence has neither subject nor predicate, then you’re most likely looking at a fragment. Think of it as a piece of a sentence.

2) ACT Grammar Rule: Don’t forget about fragments

Fragments will look like: “Went to the grocery store” or “Was okay” or “Whatever they wanted from their vacation.” Don’t they look strange on their own? Where is the subject or the predicate? Fragments will lack either.

In the ACT, you’ll be asked to then fix the fragments. Depending on the ACT grammar example, you’ll have to add the missing subject or predicate, or combine it entirely with another sentence. Make sure that you know how to spot a run-on sentence, which will improperly combine two independent clauses together and seem like too much is stuffed into one sentence.

3) ACT Grammar Rule: Know your clauses and verbs

To refresh your memory, an independent clause is a phrase that can stand on its own. A dependent clause is the opposite – it’s a phrase that contains a verb, but cannot stand on its own. It needs your help. Always look out for the subject and the corresponding verb.

There are five kinds of subjects in grammar: first-person singular, second-person singular or plural, third-person singular, first-person plural, third-person plural.

ACT English Grammar Rules (Continued)

4) ACT Grammar Rule: Verb tenses and subject-verb agreements

ACT grammar will also cover past, present, future, past perfect, present perfect, and future perfect tenses. Make sure you’re also aware of the progressive tenses, which describe a continuous action in the past, present, or future.

Progressive tenses include: past progressive tense (was talking), present progressive tense (am going), future progressive tense (will she leave), past perfect progressive (had been eating), present perfect progressive (have been enjoying), and future perfect progressive (will have been traveling)

5) ACT Grammar Rule: Gerunds and fragments (again)

Remember gerunds, the helping verb that acts as a noun? The root verb added to “ing”? The ACT grammar questions might try to trick you with gerunds in fragments, to make you think that you’re reading a complete sentence when you’re not: “Reading this on your laptop or phone, then feeling ready for the exam…” Look out for the missing subject and verb. “Reading this on your laptop or phone, you felt ready for the exam…”

6) ACT Grammar Rule: Punctuation and their exact application

The ACT will test you on your knowledge of how to use apostrophes, colons, commas, dashes, exclamation points, periods, question marks and semicolons. Are you familiar with the comma splice? The comma splice is when two run-on sentences are combined with a comma, when they should be entirely separated.

As an ACT grammar tip, try to look at every punctuation on the ACT exam and approach it as though you’re not sure if it’s supposed to be there. Should the comma be a semicolon or a period instead?

ACT Grammar Tips (Continued)

7) Modals and their relationship to verbs

It’ll be helpful to know how to spot modals on the exam, which are simply auxiliary words that come before the verb and set the tone of the sentence. Think of how it establishes the mood of the particular subject. It can be a subtle difference between “Is she going to London?” and “Should she go to London?” Or “I can stay here with you” and “I could stay here with you.” Based on the modals, you can end up with entirely different sentences.

Take some time to go over the standard modals like can, could, would, should, may, might and more. Concerning modals, the verb will remain in its pure form, without any adjustment to subject-verb agreements (like: be, go, stay, etc.)

8) ACT Grammar Rule: Modifiers (not to be confused with modals!)

In a nutshell, modifiers are the words that describe nouns. There are adjectives that modify nouns, and then there are adverbs that modify adjectives, verbs, or other adverbs. Be on the lookout for dangling modifiers also, which will often require a subject to be inserted:

Excited for my birthday, the biggest smile was on my face.

Excited for my birthday, I had the biggest smile on my face.

ACT Grammar Tips (Continued)

9) Pronouns and the pronoun-antecedent agreement

In case you need to refresh your memory, an antecedent is the subject or object in the sentence that the pronoun replaces. For example, let’s take a look at the two sentences below:

We went to three games and it was fun.

What is it referring to? Is it referring to one single game? It was should be they were: We went to three games and they were fun.

My mother was coming back from Paris with her sister and she said she loved it.

If there is an ambiguous pronoun like the one above, it is difficult to understand who the she is exactly referring to. A pronoun should always have a matching antecedent in the same sentence.

10) ACT Grammar Rule: Coordinating Conjunctions

It’s important to know how to recognize the correct use of a conjunction in a sentence, and the ACT will absolutely test you on this.

Coordinating conjunctions are used to connect two clauses of equal or similar importance. Some examples are: and, but, for, nor, or, so, yet. Take a look at this sentence: “I’d love to go swimming with you, but I promised my mom I would be home.”

ACT Grammar Tips (Continued)

11) Subordinating Conjunctions

Subordinating conjunctions are used to connect an independent clause with another independent or dependent clause that strengthens the point of the sentence. A few examples are: after, although, as soon as, because, before, if, once, since, than, that, though, unless, until, when, where, while. Try to find the subordinating conjunctions here: “I am going to buy my car as soon as I have saved enough money because I made a promise to myself.” The subordinating conjunctions are as soon as and because.

Be sure to know how to appropriately use and spot these conjunctions. The ACT will ask you questions that might trick you into thinking you want to start a sentence with “Because…” instead of “Although…” Again, it all depends on the context, so get ready to read the sentence carefully!

12) ACT Grammar Rule: Parallelism AKA parallel structure

The ACT will want to see if you can spot any inconsistencies in phrases or lists. If you are reading a sentence that lists nouns, make sure that the nouns are listed consistently and that there is no outlier that receives some extra verbs. For example, One day, I’d love to be a doctor, a lawyer, or I would also be a yoga teacher. Spot the inconsistency? The parallel structure would make the sentence into: One day, I’d love to be a doctor, a lawyer, or a yoga teacher.

Lists won’t always be in nouns; they’ll appear as verbs too. Make sure that the way the verbs and nouns are listed is consistent to the style and intention of the sentence.

13) Idioms: prepositional idioms

The ACT will test you on how well you know your idioms, but they won’t test you on figurative idioms, like how you might be feeling “under the weather.” You’ll be tested on prepositional idioms such as knowing the difference between being “worried about” something, and not “worried of.”

14) ACT Grammar Rule: Idioms: idioms with gerunds

You’ll also be tested on idioms with gerunds such as knowing how to differentiate these two sentences:

I can’t help to fall in love.

I can’t help falling in love.

15)  Idioms: two-part idioms

Make sure to also know the two-part idioms such as “not only…but also” and “neither…nor.” Practice taking ACT sample questions and read widely to see how often these idioms are used on the regular.

ACT Grammar Tips (Continued)

16) ACT Grammar Rule: Watch out for wordiness

You’ll find that sometimes the most simple answers are the right ones. Wordiness and extra words can easily complicate a sentence. Can you catch the error in that sentence? I didn’t have to write “and extra words” since I already wrote “wordiness.” The ACT will want you to choose the cleanest, most direct answer almost always.

17)  Structure in sentences and paragraphs

In the English portion of the ACT, you will be tasked with organizing the structure of sentences and paragraphs. Determine quickly what the focus of the sentence or paragraph is, and take it from there. Is there a specific tone or flow to the text? Finding that out quickly will help you organize the structure.

18) ACT Grammar Rule: Vocabulary and Transitions

The ACT will want to test you on how well you can recognize ideas transitioning between sentences or within a single sentence. Remember, transition words will indicate a direct flow. The three most common types of transition words are addition, contrast and causation.

Addition transitional words will look like: Also, moreover, likewise, in addition to…
Contrast transitional words will look like: However, in spite of, meanwhile, on the other hand…
Causation transitional words will look like: Therefore, thus, as such, because, so, as a result…

ACT English Grammar Rules (Continued)

19) Appositives: non-essential appositives and commas

Appositives are nouns or noun phrases that introduce information that helps provide a clearer picture. Take a look at the following sentence and spot the appositive:

My mother, a professor of literature, enjoys reading every night after work.

If you take out the appositive, a professor of literature, you still have a complete sentence:
My mother enjoys reading every night after work.

During the exam, make sure that the commas before and after an appositive are placed in the right place.

20) ACT Grammar Rule: Appositives: essential appositives

Unlike non-essential appositives, essential appositives do not need commas. If you were to take out the appositive here below, see what you would end up with:

Foreign secretary, John Doe, announced that he would resign.

If you take out John Doe with the commas before and after, the sentence you end up with does not make sense: Foreign secretary announced that he would resign. This means that you do not need commas when using an essential appositive:

Foreign secretary John Doe announced that he would resign.

ACT Grammar Tips – Final Thoughts 

As you prepare for the ACT, take this list of 20 ACT grammar rules as an introductory guide to getting closer to your ideal ACT score. While you don’t need to know every grammar rule in the book, it’ll be incredibly helpful for you to familiarize yourself with these fundamentals. The more you know how to recognize the grammar patterns used on the ACT, the smoother your exam journey will be.

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