Updated September 10, 2026

18 ACT Grammar Rules You Must Know for a Perfect Score

Bonus Material: PrepMaven’s ACT Score Ranges for 750+ Schools

There’s no way around it: on the ACT English section, you’ll need to be confident answering all types of grammar questions, and you’ll need to know the grammar rules inside out if you’re aiming for a high score.

The good news is that these question types are highly predictable. All you have to do is learn the rules that are being tested, and you’ll be able to handle any grammar question on the ACT.

In this post, we’ll go through 18 essential grammar rules that are tested on the ACT, plus sample questions that show you exactly how to use them.

What ACT score should you be aiming for? Take a look at our free download below, which shows the average ACT score ranges at more than 750 colleges, and find your ideal school on the list to see where your current score puts you compared to accepted applicants.

Then, keep reading for an overview of essential grammar tips you’ll need on the ACT.

Jump to section:
Combining Sentences and Phrases (Rules 1-4)
Punctuation (Rules 5-8)
Verbs (Rules 9-10)
Pronouns (Rules 11-14)
Sentence Structure (Rules 15-16)
Commonly confused words (Rules 17-18
Next steps

Combining Sentences and Phrases (Rules 1-3)

Many grammar questions you’ll see on the ACT – especially punctuation questions – come down to being able to tell the difference between independent and dependent clauses.

This is such an important skill that we’ve dedicated a whole post to it here.

In a nutshell, here’s how you can tell the difference:

Independent clauses have a verb and a subject and express a complete idea. They can stand alone.
Dependent clauses do not express a complete idea. They cannot stand alone.

Here’s an example of an independent clause:

It was annoying that the bus was delayed.

The previous sentence can stand alone. These examples, on the other hand, are not complete sentences: they don’t express a full idea.

Since I was already running late

Annoying that the bus was delayed

Notice that you can turn an independent clause into a dependent one by adding a conjunction: “the class took the test” is an IC, but “while the class took the test” is a DC, because it doesn’t express a full idea. You won’t need to transform clauses on the ACT, but keeping an eye out for conjunctions that introduce clauses can help you tell the difference between an IC and a DC.

On the ACT, your understanding of clause types is mainly tested through questions about punctuation rules. That’s why, on any sentence-level punctuation question, you should always start by figuring out how many clauses there are and what kind of clauses they are.

Rule #1: To combine two independent clauses, use a hard break (period, semicolon, or colon) or a comma + FANBOYS

There are 2 – and only 2! – ways to combine two independent clauses.

One is to use a hard break between the two ICs. That means a semicolon, colon, or period.

I was already running late. It was annoying that the bus was delayed.

I was already running late; it was annoying that the bus was delayed.

The other way to join two ICs is to use a comma followed by one of these conjunctions: for, and, nor, but, or, yet, so. You can remember them using the acronym FANBOYS.

I was already running late, so it was annoying that the bus was delayed.

Whatever you do, do not just put a comma between two ICs. This is called a comma splice. It’s one of the most common pitfalls when it comes to punctuation rules, and it’s a common incorrect answer choice offered.

Here are the options for joining two independent clauses in a nutshell:

IC ; IC (Semicolons separate two ICs)
IC . IC (Periods separate two ICs)
IC : IC (Colon separates two ICs)
IC , FANBOYS IC (Comma + Fanboys separates two ICs)
NEVER: IC , IC (Comma cannot separate two ICs)

How do you choose between multiple correct answer choice options on the ACT? That part is easy: you’ll never have to.

There will only ever be one correct answer choice, so a question where you have to join 2 independent clauses will never give you both a semicolon and a period, for example.

Rule #2: To combine an independent and a dependent clause, use a comma.

So what about joining a dependent clause and an independent clause?

In this case, you can use just a comma – no need for a FANBOYS conjunction.

What about hard stops: colons, semicolons, and periods?

Because hard stops only come after a complete idea, you cannot use a hard stop – semicolon, colon, or period – to separate a DC from an IC.

Take a look at these two examples. The first one has a DC before the IC.

Since I was already running late, it was annoying that the bus was delayed.

And this one has an IC before a DC:

It was annoying that the bus was delayed, since I was already running late.

Rule #3: Use a comma after an introductory phrase.

As well as independent and dependent clauses, you’ll also encounter supplementary phrases (SPs). These not only don’t express a full idea – they don’t even include a subject and a verb.

Use a single comma to set off an introductory phrase before an independent clause.

In these examples, the SPs are in bold.

By midnight, I had finally finished the essay.

Fluttering to the ground, the pages fell from his hand.

The pages, fluttering to the ground, fell from his hand.

As you can see from the examples, you use a single comma to separate an SP from an IC if it comes first. If the SP interrupts the IC, then you’ll want two commas. That’s because a subject and a verb can only ever be separated by 0 commas or by 2 – never just by 1!

Rule #4: Use 2 commas or 2 dashes to separate non-essential info in a sentence.

There’s overlap here with Rule #3 about combining a phrase with an independent clause. It’s listed as a separate rule, though, because it applies to all non-essential info, not just phrases.

Within one independent clause, the subject and the verb can be separated by 2 commas or dashes – but never just by 1.

So, when you’re inserting a phrase in a sentence between the subject and the verb, make sure that you use 2 commas or dashes, one on either side.

Note that “non-essential” here means it’s grammatically non-essential: the sentence would still be complete – with a subject, verb, and a complete idea – if you crossed out the section between commas or dashes. It has nothing to do with whether the info is essential to the meaning of the sentence.

Here’s what that looks like:

The pages, fluttering to the ground, fell from his hand.

My dog, however, had other ideas.

We were so late – over three hours – that we missed the entire movie.

To figure out if this rule applies to a sentence on the ACT, try crossing out the words that would be between commas or dashes. Does the sentence still make sense grammatically?

And for more practice of all the ways dashes can be used, look at our post on using colons and dashes on the ACT.

Practice Questions: Combining Sentences and Phrases

1. The concert tickets sold out quickly, the fans were disappointed.

A) NO CHANGE
B) The concert tickets sold out quickly so the fans were disappointed.
C) The concert tickets sold out quickly; the fans were disappointed.
D) The concert tickets sold out quickly the fans were disappointed.

2. The professor gave a lecture on climate change, explaining the causes and effects in detail.

A) NO CHANGE
B) The professor gave a lecture on climate change and explaining the causes and effects in detail.
C) The professor gave a lecture on climate change explaining the causes and effects in detail.
D) The professor gave a lecture on climate change, and explaining the causes and effects in detail.

3. Although the weather was cold we decided to go for a hike.

A) NO CHANGE
B) Although the weather was cold, we decided to go for a hike.
C) Although the weather was cold, but we decided to go for a hike.
D) We decided to go for a hike, although the weather was cold.

Answer Key:

C. These are two independent clauses. Independent clauses must be joined with either a hard stop (semicolon, colon, or period) or comma plus a FANBOYS conjunction.
A. Here, we’re looking at an independent clause followed by a supplementary phrase. “Explaining the causes and effects in detail” is a phrase that provides additional information about the lecture. The correct way to join this phrase with the independent clause is by using a comma.
B. This is a dependent clause followed by an independent clause, so we need a comma in between them. (If the DC came after the IC, we wouldn’t need a comma — but since it comes before, we do.)

Punctuation (Rules 5 – 7)

Combining clauses and phrases isn’t the only area on the ACT where you’ll need to know punctuation rules. Here are the other essential punctuation rules to know.

Rule #5: Use commas to separate items in a list, or semicolons for items in a list with commas.

When you’re listing multiple items, put a comma after each one, including a comma before the final “and.”

We picked up bagels, muffins, and a loaf of banana bread for the brunch meeting.

If any of the items in a list contain commas themselves, then put semicolons between each item to avoid confusion about where each list item ends. You should do this even if only one item has a comma, like in the second example below.

On our road trip, we passed through Mansfield, MO; Independence, KA; Walnut Grove, NE; and De Smet; SD.

The scientists on the research team included a biologist; an organic chemist, who led the team; and a physicist.

For more detail on comma rules, check out our post specifically on this topic.

Rule #6: Use apostrophes to make singular and plural nouns possessive.

To show ownership, add an apostrophe to the ending of a noun.

You need to add an apostrophe plus s (‘s) if:

The noun is singular (even if it already ends in s!).
The noun is plural, but its plural form does not end in s.

You only add the apostrophe, with no s, if:

The noun is plural and ends in s.

Here’s what that looks like in practice.

	Apostrophe + s	Apostrophe with no s
Singular noun not ending in s	Ellie’s flute My teacher’s methods
Singular noun ending in s	Chris’s book The pass’s expiration date
Plural/collective noun not ending in s	The children’s schedule People’s opinions
Plural/collective noun ending in s		Schools’ curriculum Dairy cows’ living conditions

This can be confusing, so we’ve dedicated an entire post to the different ways apostrophes are used here.

Rule #7: Use apostrophes to form contractions – and always check your work by expanding contractions.

Apostrophes are also used for contractions: combinations of two or more words where one or more letters are deleted. In that case, the apostrophe replaces the missing letters.

To get back to the original phrase, fill in the letters that the apostrophe is replacing.

They’re → they are
We’ve → we have
You’re → you are

Expanding is helpful to tell contractions apart from words that sound the same but mean something different (which are often possessives). Here are some of the most common ones to watch out for.

“You’re” means “you are.” “Your” is possessive.
“It’s” means “it is.” “Its” is possessive.
“They’re” means “they are.” “Their” is possessive, and “there” indicates place.
“Who’s” means “who is.” “Whose” is possessive.

Rule #8: Use a colon or a single long dash to indicate a new thought or shift in direction – and make sure it’s preceded by a complete sentence.

In this case, colons and single long dashes are functioning essentially in the same way.

Colon and single long dash usage on the ACT basically boils down to your ability to identify complete and incomplete sentences. When it comes to using these punctuation marks properly, it’s particularly important to know what makes up a complete sentence. That’s because of this one important colon rule:

The sentence that precedes a colon or a long dash must be complete.

It doesn’t matter what comes after a colon or single long dash, really–incomplete sentence, complete sentence, a phrase, a single word. All that matters is that the sentence that comes before the punctuation mark is complete. That’s it!

With long dashes, be careful not to get tripped up by pairs of long dashes, which are used differently from single long dashes.

Remember that this only applies to a single long dash. A pair of long dashes setting of non-essential information does not need to come after a complete sentence (and, in fact, it must come within a sentence).

Here’s an example of a single long dash functioning much like a colon. Notice how the sentence that comes before the long dash is a complete sentence and that what comes after the long dash is a new thought or elaboration.

That’s just it—we don’t know all of the answers to the questions of the universe.

To test for proper use of the single long dash, see if you can replace it with a colon. If you can (i.e., if that sentence on the left of the punctuation is complete), then the single long dash is permissible.

Practice Questions: Punctuation

1. The store sells apples; bananas; oranges; and pears.

A) NO CHANGE
B) The store sells apples, bananas, oranges and pears.
C) The store sells apples; bananas; oranges and pears.
D) The store sells apples, bananas, oranges, and pears.

2. The children’s toys were scattered all over the yard.

A) NO CHANGE
B) The childrens’ toys were scattered all over the yard.
C) The childrens toys were scattered all over the yard.
D) The childrens’s toys were scattered all over the yard.

3. Frances’s book and the kids’s crayons were still in the car.

A) NO CHANGE
B) Frances’s book and the kids’ crayons were still in the car.
C) Frances’ book and the kids’ crayons were still in the car.
D) Frances’ book and the kids’s crayons were still in the car.

4. The teacher, on the other hand was running late.

A) NO CHANGE
B) The teacher on the other hand was running late.
C) The teacher on the other hand, was running late.
D) The teacher, on the other hand, was running late.

5. I found the dog’s leash, but I couldn’t find it’s harness.

A) NO CHANGE
B) I found the dog’s leash, but I couldn’t find its harness.
C) I found the dogs’ leash, but I couldn’t find its harness.
D) I found the dogs’ leash, but I couldn’t find it’s harness.

6. Take Bartlett pears, for instance, unless they are treated with exactly the right amount of 1-MCP at exactly the right time, they will remain hard and green until they rot.

A) NO CHANGE
B) pears, for instance:
C) pears for instance,
D) pears. For instance,

Answer Key:

D. For items in a list, you use commas (you only use semicolons if the items themselves contain commas). There are different styles on whether to use a comma before the final “and,” but on the ACT, you’re expected to use on.
A. To make irregular plural nouns possessive, just add an apostrophe plus s.
B. Singular names that end in s, like Frances, still get an ‘s added to them when they’re possessive! But plural nouns that end in s do not, so kids’s would be redundant: kids’ is all you need.
D. We’re looking at a phrase inserted into an independent clause to add some non-essential information. Remember that the subject (teacher) and the verb (was) can be separated by 0 commas or by 2, but never but 1. So you’ll need 2 commas here, one on either side of the inserted phrase.
B. Its is the possessive form of it. It’s is the contraction of it is. Since we’re only talking about one dog, the apostrophe comes before the s in dog’s.
B. “For instance” is a transition phrase. We know that phrases require 1-2 commas, depending on where they appear in the sentence. At the very least, we’ll want a comma before the “for.” This helps us eliminate answers C and D. How do we decide between A and B? Let’s apply our knowledge of complete and incomplete sentences. “Take Bartlett pears, for instance” is a complete sentence. So is “unless they are treated…them again.” We know that we can’t combine 2 complete sentences with just a comma, so B is our answer.

Verbs (Rules 9-11)

Rule #9: Make sure the verb tense is consistent throughout an independent clause.

The verb tense shouldn’t change within one independent clause. Usually, this means it shouldn’t change within a sentence.

These sentences are both correct:

I finished my book and started deciding what to read next.

I finish my book and start deciding what to read next.

Mixing and matching verb tenses is not correct:

I finished my book and start deciding what to read next.

Like with subject-verb agreement (see rule 8), this isn’t a hard concept by itself – but the test makers often put lots of extra fluff in sentences for verb tense questions. When multiple verbs in a sentence are separated by unnecessary extra information, you can lose sight of what all the verbs were and whether they match.

On verb tense questions, find and circle all the verbs in the sentence to make sure they match. The correct answer choice is the one where the verbs are in the same tense.

Rule #10: Make sure the subject and the verb match in number.

This is called “subject-verb agreement.” In its basic form, it’s probably already intuitive for you.

This sentence has subject-verb agreement:

Lars picked up bagels for brunch.

This sentence doesn’t, so it is not a correct sentence:

Lars pick up bagels for brunch.

So why can this be a tricky topic on the ACT? Because, on trickier subject-verb agreement questions, lots of extra fluff will be stuffed in between the subject and the verb. By the time you get to the verb, the subject might not be fresh in your mind, or you might be confused about which word it is.

To tackle subject-verb agreement questions where you’re being asked for the correct verb form, identify the subject and the verb in the sentence and cross out all the “fluff,” mentally or on the page. Then ask yourself whether they match.

Lars ~~drove in circles for fifteen minutes looking for parking, got extremely frustrated, and almost gave up, but, finally, thanks to an opening down the street from the bakery~~, picked up bagels for brunch.

Practice Questions: Verbs

1. After getting home late, Sarah quickly finished her homework, had a snack, and brushed her teeth, and by the time her parents got home, she’s fast asleep.

A) NO CHANGE
B) and by the time her parents got home, she’ll be fast asleep.
C) and by the time her parents get home, she’s fast asleep.
D) and by the time her parents got home, she was fast asleep.

2. Jenna and I, despite our differences in opinion, usually manages to find some common ground.

A) NO CHANGE
B) Jenna and I, despite our differences in opinion, usually has managed to find some common ground.
C) Jenna and I, despite our differences in opinion, usually managed to find some common ground.
D) Jenna and I, despite our differences in opinion, usually managing to find some common ground.

Answer Key:

D. This question is testing verb tense consistency. Because the sequence of events is described in the past tense, the final verb should also be in the past tense.
C. This question is testing subject-verb agreement. “Jenna and I” is a plural subject, so the verb also needs to be plural.

Pronouns (Rules 11-14)

Rule #11: Make sure pronouns and antecedents match in number and gender.

This concept is similar to subject-verb agreement, except that the things you need to match are pronouns and antecedents.

To recap: a pronoun is a word that takes the place of a noun. “She” is a pronoun that could be referring back to a person named earlier. “It” could refer back to any object that was mentioned earlier.

An “antecedent” is just a fancy way of saying “that thing that was mentioned before.” In this example sentence, “they” is a pronoun and “the students” is the antecedent.

After the students finished their homework, they eagerly hurried to the theater to see the new movie.

If a question involves different options for a pronoun, you may be looking at a pronoun-antecedent question. These are the ways pronouns and antecedents must match:

Number (singular or plural)
Gender (masculine, feminine, or neuter)

A related point is to avoid ambiguous pronouns. In the first sentence here, it’s not clear what “her” refers to – Mary’s book or Diane’s book. In the second sentence, it’s been made clear.

Repeating the name may seem redundant, but especially in more complicated sentences, it can be important to clarify what’s going on.

Mary told Diane her book seemed interesting.

Mary told Diane Mary’s book seemed interesting.

Rule #12: Keep pronoun use clear and consistent within a sentence.

In the first sentence here, it’s not clear what “her” refers to – Mary’s book or Diane’s book. In the second sentence, it’s been made clear.

Mary told Diane her book seemed interesting.

Mary told Diane Mary’s book seemed interesting.

Repeating the name may seem redundant, but especially in more complicated sentences, it can be important to clarify what’s going on.

The same goes for keeping pronoun use consistent throughout a sentence. In general, if you start out with one pronoun in a sentence, you have to stick with it. This is especially important when using the pronouns “you” and “one.”

For example, this is an example of pronoun inconsistency (which would be incorrect on the ACT):

If you keep walking for about five blocks, one will spy a curious sight.

Both “you” and “one” in this sentence technically refer to the same general individual, but we need to use one or the other (not both). Here is a correct version of this sentence that shows pronoun consistency:

If you keep walking for about five blocks, you will spy a curious sight.

Rule #13: Distinguish between subject and object pronouns.

A common mistake many people make in casual speech is to confuse subject and object pronouns.

The table below shows the different pronoun forms for each person.

The subject pronoun should be the person doing the action. If there’s more than one person, the pronouns can be combined. These are correct sentences:

I went to the beach.

Mom and I went to the beach.

He and I went to the beach.

Make sure that you don’t put an object pronoun in here as the subject. These sentences are both incorrect:

Me and Jake went to the beach.

Him and I went to the beach.

On the flip side, if a pronoun is the object of the verb, meaning the action is being done to it, then it should be an object pronoun. The most common mistake here is to use “I” instead of “me.”

He saw Mom and I at the beach. (incorrect)

He saw Mom and me at the beach. (correct)

On the ACT, this skill will usually be tested by using plural subjects or objects. To simplify the question, get rid of the fluff. “Me and Jake went to the beach” might sound okay, but when you simplify it to “Me went to the beach,” you’ll instantly hear the mistake.

Subject Pronoun	Object Pronoun	Possessive Adjective	Possessive Pronoun	Reflexive Pronoun
I	me	my	mine	myself
you	you	your	yours	yourself / yourselves
we	us	our	ours	ourselves
they	them	their	theirs	themselves
she	her	her	hers	herself
he	him	his	his	himself
it	it	its	n/a	itself

Rule #14: Distinguish between “that” and “which.”

We use the terms that and which frequently. What’s the difference?

First, both are used to refer to objects, not people. You can only use “who” or “whom” to refer to people.

For the purposes of the ACT, the difference comes down purely to punctuation: which generally has a comma in front of it, while that does not require a comma or any intervening punctuation.

Here are two examples that make this clear:

He told me that I would have to drop a class in order to maintain my grades.

Cooper Park, which is just a half mile from campus, is a popular destination for students and dog-walkers.

Practice Questions: Pronouns

1. My sister told our mom her appointment was on Tuesday.

A) NO CHANGE
B) My sister told our mom my sister’s appointment was on Tuesday.
C) My sister told her her appointment was on Tuesday.
D) She told our mom her appointment was on Tuesday.

2. I asked my brother if he wanted to come to the show with me, but him and our mom, after a long day driving to our grandma’s house and back, were too tired and decided to pass.

A) NO CHANGE
B) but he and our mom
C) but they
D) but our mom and him

Answer Key

B. This question is testing pronoun-antecedent matching and clarity. Because “her” could be referring either to the sister or to the mom, this sentence’s meaning is unclear. You’ll want to specify who “her” refers to. (Note that “My sister told our mom our mom’s appointment was on Tuesday” would also be correct – which is why it’s not an option. You’ll only ever see one correct answer choice for each question.)
B. This question is testing subject and object pronouns. “Him and our mom” cannot be the subject of “were too tired and decided to pass,” because “him” is an object pronoun. The correct subject pronoun is “he.” (Why is C incorrect? Because the speaker only asked “my brother” if he wanted to come, so we need a pronoun that refers specifically back to him. “They” does not refer back to “my brother.”)

Sentence Structure Rules (Rules 15-16)

Rule #15: Put modifiers right next to what they’re modifying and avoid dangling modifiers.

A modifier is a word or phrase that provides more information about a specific entity in a sentence.

On the ACT, you’ll usually see modifiers in the form of short phrases with gerunds (words ending in -ing). In these correct sentences, the bolded phrases are modifiers.

Having studied biology, my mother now worked as a marine biologist.

My mother, having studied biology, had decided that it wasn’t the career path for her.

Getting home late, we decided to order pizza instead of cooking.

A modifier should go right next to what it’s modifying. Otherwise, it’s called a “dangling modifier,” like in these sentences:

Having studied biology, my mother’s job was in the marine biology department of the local university.

Getting home late, pizza sounded like a great idea.

In these last two sentences, the misplaced modifiers make it sound like “my mother’s job” had studied biology (not my mother) and “pizza” had gotten home late (not the people who ordered it).

Modifier questions are more common on the ACT than on the SAT, so if you’re taking both tests or you’ve taken the SAT before, you might want to brush up on your modifier practice before taking the ACT.

Rule #16: Use parallel structure for comparisons or list items.

Parallelism isn’t just a concept that appears in math. It also concerns grammatical structure, especially with respect to comparisons or lists. Basically, parallelism in the world of English grammar involves making sure everything matches!

To apply parallel structure, ensure that items in a comparison or list are in the same form, category, and/or number. A list includes three or more words or phrases separated by commas. A comparison involves 2 words or phrases and may include the word “than.”

In this next example, the verbs in the list all have the same form (-ing):

Desmond spends his days at the library photocopying, transcribing, and cataloguing articles.

Here, the nouns in the list are all singular, reflecting parallelism in number:

Someday I hope to invest in a car, a retirement account, and a rental property.

Yes, it would be technically grammatically incorrect to list out a mixture of singular and plural nouns (i.e., Someday I hope to invest in a car, several homes, a retirement account, and three rental properties).

How do you know if you have a parallelism question on your hands on the ACT? Be on the lookout for the word “than” in the sentence’s context, as this indicates a comparison. If you see a list, scan the answer choices and identify what’s different between them, as lists can be fair game for comma rule application or parallelism.

Practice Questions: Sentence Structure

1. Arriving just in time, the movie started as we were taking our seats.

A) NO CHANGE
B) we were taking our seats as the movie started.
C) the movie started as we took our seats.
D) the movie was starting as we were taking our seats.

2. Des enjoyed collecting stamps, state quarters, and he also had an impressive postcard collection.

A) NO CHANGE
B) and also an impressive postcard collection.
C) and postcards.
D) and collecting postcards.

Answer Key:

B. The original sentence has a dangling modifier: because “the movie” comes right after “arriving just in time,” it sounds like the movie arrived just in time, which doesn’t make sense. You need to rearrange the order of the sentence to put the modifier next to what it’s modifying.
C. We need this list to be parallel, so the third list item should be the thing that Des collected, like the first two.

Commonly Confused Words (Rules 17-18)

Rule #17: Know your idioms, especially prepositional phrases.

Sometimes, the ACT will test your knowledge of idioms, especially prepositional idioms. You’ll be asked which preposition goes with a verb or noun.

Most of these two-part idioms will be familiar to native English speakers. If you’re an English learner or if you feel like you could use some review of prepositional phrases, this list summarizes some of the most common ones to know.

accustomed to
associated with
curious about
necessary for
at last
in general
as a means of
by all means
from time to time

Rule #18: Look out for commonly confused words and homonyms.

Sometimes, ACT questions will test your ability to distinguish between homonyms, two words that sound the same but have different spellings and meanings.

Some of these involve contractions that we saw earlier.

“You’re” means “you are.” “Your” is possessive.
“It’s” means “it is.” “Its” is possessive.
“They’re” means “they are.” “Their” is possessive, and “there” indicates place.
“Who’s” means “who is.” “Whose” is possessive.

Here are some other commonly confused words you might see.

“Than” is used for comparisons (“I read less than she does.”) “Then” refers to time or the order in which something is happening (“I’ll go to the library and then to the bank.”)
“Affect” is usually a verb and “effect” is usually a noun. (Not always, but on the ACT, this is a pretty safe bet.)
“Compliment” is a nice thing to say to someone (“He complimented my poetry.”). “Complement” means something goes well with something else (“The online practice questions complement the textbook”; “The color of the flowers complemented her eyes.”).

Practice Questions: Commonly Confused Words

1. The school’s students were accustomed with heavy traffic on the way to school in the mornings.

A) NO CHANGE
B) accustomed into
C) accustomed to
D) accustomed for

2. I don’t know why they think they’re project idea is better than ours.

A) NO CHANGE
B) their
C) there
D) you’re

3. Everyone loves Jordan’s poetry, but luckily, he doesn’t let compliments effect his ego.

A) NO CHANGE
B) complements effect
C) complements affect
D) compliments affect

Answer Key:

C. “Accustomed” requires the preposition “to.”
B. “They’re” is a contraction of “they are.” “Their” is the possessive, which is what you need here. “There” refers to place. “You’re” is a contraction of “you are,” so it can never be possessive (“your” could have been correct, but that wasn’t an option).
D. A “compliment” is a nice thing to say; “complement” means, among other things, to go well together. “Effect” is usually a noun, and what we need here is a verb: “affect.”

Next Steps

Now that you know the fundamentals for ACT grammar questions, the next step is to practice.

We’ve put together a complete guide to preparing for the test. And if you want extra support with any section of the test, consider getting in touch with our team for a free consultation.

Curious what score you should be aiming for? This spreadsheet shows the median and 25th and 75th percentile ACT scores for more than 750 colleges and universities. Find the colleges you’re applying to on the list to set your goal score and start working towards it.

18 ACT Grammar Rules You Must Know for a Perfect Score

18 ACT Grammar Rules You Must Know for a Perfect Score

Combining Sentences and Phrases (Rules 1-3)

Rule #1: To combine two independent clauses, use a hard break (period, semicolon, or colon) or a comma + FANBOYS

Rule #2: To combine an independent and a dependent clause, use a comma.

Rule #3: Use a comma after an introductory phrase.

Rule #4: Use 2 commas or 2 dashes to separate non-essential info in a sentence.

Practice Questions: Combining Sentences and Phrases

Punctuation (Rules 5 – 7)

Rule #5: Use commas to separate items in a list, or semicolons for items in a list with commas.

Rule #6: Use apostrophes to make singular and plural nouns possessive.

Rule #7: Use apostrophes to form contractions – and always check your work by expanding contractions.

Rule #8: Use a colon or a single long dash to indicate a new thought or shift in direction – and make sure it’s preceded by a complete sentence.

Practice Questions: Punctuation

Verbs (Rules 9-11)

Rule #9: Make sure the verb tense is consistent throughout an independent clause.

Rule #10: Make sure the subject and the verb match in number.

Practice Questions: Verbs

Pronouns (Rules 11-14)

Rule #11: Make sure pronouns and antecedents match in number and gender.

Rule #12: Keep pronoun use clear and consistent within a sentence.

Rule #13: Distinguish between subject and object pronouns.

Rule #14: Distinguish between “that” and “which.”

Practice Questions: Pronouns

Sentence Structure Rules (Rules 15-16)

Rule #15: Put modifiers right next to what they’re modifying and avoid dangling modifiers.

Rule #16: Use parallel structure for comparisons or list items.

Practice Questions: Sentence Structure

Commonly Confused Words (Rules 17-18)

Rule #17: Know your idioms, especially prepositional phrases.

Rule #18: Look out for commonly confused words and homonyms.

Practice Questions: Commonly Confused Words

Next Steps

Related ACT Posts