Even though the English language is complex, ACT English tests a specific set of grammar rules. Furthermore, it tests these rules the same way, over and over again.
In this complete guide, we've compiled the comprehensive list of ACT English grammar rules you need to know to ace the ACT English section. If you master all these rules and practice them with realistic ACT questions, you'll have a huge advantage on the English section.
Unlike other guides, we give you lots of examples to help you understand how the grammar rule will show up on the ACT. After all, you need to master the ACT format to do well on the ACT.
The writing rules tested on the ACT can be grouped into two categories: Usage and Rhetoric.
Usage skills are what you classically call "Grammar Rules," such as punctuation, subject/verb agreement, verb tenses.
Rhetorical skills have to do with style, organization, and writing logic. You'll need to learn how to organize sentences in a paragraph, how to connect two ideas together logically, and how to sequence paragraphs together.
We'll start first with Usage skills, then onto Rhetorical skills.
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Usage questions cover primarily grammar and punctuation — what we generally think of as correct English.
The ACT only tests very specific uses of certain kinds of punctuation. Those rules, and only those rules, are detailed below.
Use commas to separate words and word groups in a simple series of three or more items.
We had coffee, cheese, crackers, and grapes.
Use a comma to separate two adjectives when the adjectives are interchangeable.
It was a vibrant, massive painting.
When starting a sentence with a dependent clause, use a comma after it.
When Jim studied in the library for his chemistry quiz, it was very quiet.
Use commas to set off nonessential parts of the sentence.
The woman, knowing it was late, hurried home.
Apostrophes are used two ways on the ACT: to show possession and to create contractions. Many of the apostrophes issues are tested using the "Word Choice" skill further below.
To form possessives of nouns:
The kids' toys
The tree's leaves
Note that the singular possessive Laura's has the apostrophe before the s, while the plural possessive kids' has the apostrophe after the s.
To create contractions (show the omission of letters):
There's a clown.
You'd love it.
Use a colon after an independent clause when it is followed by a list, a quotation, appositive, or other idea directly related to the independent clause.
The vote was unanimous: the older candidate had won.
Use a semicolon to join 2 independent clauses when the second clause restates the first or when the two clauses are of equal emphasis.
I'm not sure how to get there; let's get directions.
Use a semicolon to join 2 independent clauses when the second clause begins with a conjunctive adverb (however, therefore, etc.) or a transition (in fact, for example, etc.).
The basement is scary; thus, I do not go down there alone.
Dashes are used to set off or emphasize the content enclosed within dashes or the content that follows a dash. Dashes place more emphasis on this content than parentheses.
Upon discovering the errors—all 124 of them—the publisher immediately recalled the books.
Use a period at the end of a sentence that makes a statement.
He will try again.
Use a question mark after direct questions.
Where are we?
Use (rarely) an exclamation point at the end of a sentence to express strong emotion.
A pronoun is a noun that can stand in for another noun. For example, the pronoun "she" can stand in for "the woman" or "Queen Elizabeth." But, unlike nouns, pronouns change their form if they're used in different ways. These are the ways that pronouns are tested on the ACT.
Subject vs. Object Pronouns
Nouns, in relation to verbs, can be subjects or objects. Subjects "do" verbs and objects have verbs "done" to them: a dog (the subject noun) chases (the verb) its tail (the object noun).
Regular nouns like dog or tail do not change depending on whether they are subjects or objects, but most pronouns do. For example, in the phrase "she likes him," the woman is the subject, so the pronoun is she; in the phrase "he likes her," the woman is the object, so the pronoun is her.
Error: Me and my parents ate dinner.
Corrected: My parents and I ate dinner.
Error: The tourists asked my friends and I for directions.
Corrected: The tourists asked my friends and me for directions.
Error: The Girl Scouts sold cookies to my sister and I.
Corrected: The Girl Scouts sold cookies to my sister and me.
Note above that all of the examples pair the faulty pronoun with another noun. This is almost always how the harder ACT pronoun questions test this skill.
This concept is simple: who is the pronoun for a person or people, and that is the pronoun for everything else.
Error: The coach is the person that is in charge of the team's schedule.
Corrected: The coach is the person who is in charge of the team's schedule.
Error: The elephant is the animal who asks for the most treats.
Corrected: The elephant is the animal that asks for the most treats.
Error: The corporation is who owns this land.
Corrected: The corporation is what owns this land.
When we use pronouns more than once in a sentence, we have to use the same perspective throughout.
Error: If a person wants to succeed in corporate life, you have to know the rules of the game.
Corrected: If a person wants to succeed in corporate life, she has to know the rules of the game.
Error: Everyone should make their own decision.
Corrected: Everyone should make his own decision.
Error: Every student must study hard if they want good grades.
Corrected: Every student must study hard if she wants good grades.
Note: In the second example, that the error is the commonly-used "their" to mean a singular noun (everyone); while this is used in common, everyday speech, using "their" as a possessive pronoun for a single person is not formally accepted as grammatically correct on the ACT. These singular nouns that seem plural (such as nobody, anyone, and each person), as well as "their" instead of the singular "he" or "his," are often tested in the hardest pronoun questions.
Wherever there is a pronoun, it should be obvious what the pronoun is "standing in" for.
Error: Ethel told Lucy that her pie was wonderful.
Corrected: Ethel told Lucy that Lucy's pie was wonderful.
Error: The files arranged by the temporary workers were out of order, so we sent them back to the main office.
Corrected: The files arranged by the temporary workers were out of order, so we sent the files back to the main office.
Error: Once Nora and Elise go to live with their husbands, they have to convert to their ways of living.
Corrected: Once Nora and Elise go to live with their husbands, the husbands have to convert to their wives' ways of living.
Verb Forms: Tense and Agreement
There are six basic verb tenses, two for each time period:
- Simple Present: They sing.
- Present Perfect: They have sung.
- Simple Past: They sang.
- Past Perfect: They had sung.
- Future: They will sing.
- Future Perfect: They will have sung.
All of these tenses are created out of three forms of "to sing": sing (present), sang (past), and sung (past participle). As you can see, some of the correct verb forms are created by adding forms of the words "have" and "do." The idea is to keep verbs in a single sentence within the same time period.
Error: The boy insisted that he has paid for the candy bars.
Corrected: The boy insisted (past) that he had paid (past perfect) for the candy bars.
Error: The doctor suggested bed rest for the patient, who suffers from a bad cold.
Corrected: The doctor suggested (past) bed rest for the patient, who suffered (past) from a bad cold.
Error: I told him that he can drop by any time and I will be happy to help him.
Corrected: I told (past) him that he could (past) drop by any time and I would (past) be happy to help him.
Nouns and verbs are both parts of speech with number: they are written differently if they refer to just one thing or multiple things. Subject/verb agreement just means that the noun and the verb have the same number (singular or plural). For example, one dog runs fast, but two dogs run fast.
Matching subjects and verbs are underlined, while verbs that don't match subjects are bold.
Error: The climate in those cities are uncomfortably humid.
Corrected: The climate (singular) in those cities is (singular) uncomfortably humid
Error: There was a rat and three buckets of whitewash in the corner of the basement.
Corrected: There were (plural) a rat and three buckets of whitewash (plural) in the corner of the basement.
Error: Ms. Russell is trying to read a book outside but a swarm of flies keep distracting her.
Corrected: Ms. Russell is trying to read a book outside but a swarm (singular) of flies keeps (singular) distracting her.
These are pretty simple. Comparisons between two things are formed by the construction "x is more/less [adjective]/[adjective]-er than y." For example, Bill is more friendly than Louis.
Comparisons between three or more things, however, are formed by the construction "x is the most [adjective]/[adjective]-est of the [things]." For example, Lucy was the most adept student in the class or The cheetah is the fastest land animal.
The ACT tests this skill by mismatching the types of comparison:
Error: Between butterflies and spiders, humans admire butterflies the most.
Corrected: Between butterflies and spiders, humans admire butterflies more.
Error: Cheetahs are the faster of all land mammals.
Corrected: Cheetahs are the fastest of all land mammals.
Error: Nationalists think theirs is the better nation of all.
Corrected: Nationalists think theirs is the best nation of all.
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These questions are about commonly confused words. Just memorize which is which.
Its vs. It’s
It's is short for it is or it has.
It's too late.
Its shows possession, like his and her.
These are its footprints.
Their vs. There vs. They’re
There refers to a place.
There is a terrarium in the first building; it is over there.
They're is a contraction of they are.
They're not in this building.
Their is the possessive pronoun.
Their house is on the next street.
To vs. Too vs. Two
Two is a number.
There were two books on the table.
Too means "more than enough" and "also."
After we got our dinner for free, they gave us too much ice cream for dessert, too!"
To indicates direction and action.
We're going to the park to play basketball.
Then vs. Than
Then is mainly an adverb, often used to situate actions in time.
That was then; this is now.
Than is a conjunction used mainly in making comparisons.
Shaq is taller than Kobe.
"Might have" vs. "Might of"
"Might have" is correct. "Might of" is not.
She might have gotten lost.
Idioms are expressions that mean something different than the actual words they use, such as "rain cats and dogs" or "kick the bucket." But in English we also have short phrases made of words that always go together, and these are also tested on the ACT.
Error: Maria stumbled in her old rocking horse in the garage.
Corrected: Maria stumbled upon her old rocking horse in the garage.
Error: Loud guard dogs keep burglars in bay.
Corrected: Loud guard dogs keep burglars at bay.
Error: Arturo and I happened for meet at the library.
Corrected: Arturo and I happened to meet at the library.
The ACT particularly loves one type of idiom: verbal phrases, which are verb + preposition pairs. They always want to know if you know which is the correct preposition, as in the incorrect sentences below.
Error: The show was followed on an encore.
Corrected: The show was followed by an encore.
Error: She is responsible of returning her library books.
Corrected: She is responsible for returning her library books.
Error: One should refrain for texting while driving.
Corrected: One should refrain from texting while driving.
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Sentence Fragments & Run-on Sentences
Sentences are made up of groups of words that are called clauses. There are two types of clauses: independent (can be a complete sentence) and dependent (must be attached to an independent clause in order to be a complete sentence).
An independent clause has a subject-verb pair and does not start with a word or phrase that makes the clause dependent, such as "when" or "because" (as in example 3 below).
In the examples below, the subjects are underlined and the verbs are in bold.
A Sentence Fragment is a sentence made of anything less than an independent clause. To fix it, we add an independent clause.
Fragment: Such as electrical, chemical, and industrial engineering.
Corrected: There are many STEM careers, such as electrical, chemical, and industrial engineering.
Fragment: Saving her team at a time when they needed her.
Corrected: The goalie was saving her team at a time when they needed her.
Fragment: Because the one I have now isn't working out too well.
Corrected: I need a new roommate, because the one I have now isn't working out too well.
A Run-on Sentence is made of multiple independent clauses joined by only a comma or no punctuation at all. It can be fixed with a comma and conjunction (example 1 below), a joining word like and or because (example 2 below), or a semicolon (example 3 below).
Run-on sentence: My favorite Mediterranean spread is hummus it is very garlicky.
Corrected: My favorite Mediterranean spread is hummus, as it is very garlicky.
Run-on sentence: I rushed out to the shop, I had no milk left.
Corrected: I rushed out to the shop because I had no milk left.
Run-on sentence: Mary likes dogs she has a beagle.
Corrected: Mary likes dogs; she has a beagle.
Parallel construction is when we present a list of things all in the same way. For example, if two things in a list are adverbs, the third should also be an adverb. If two things in a list are "to [verb]," then the other should also be in the form "to [verb]." To fix it, we just phrase all of the items in the list the same way.
Error: The couple bought the concert tickets, arrived at the theater, and went about finding their seats.
Corrected: The couple bought the concert tickets, arrived at the theater, and found their seats.
Error: The deer moved carefully, quietly and in a way that was slow.
Corrected: The deer moved carefully, quietly and slowly.
Error: Peeling hazelnuts requires skill, patience, and the ability to persevere.
Corrected: Peeling hazelnuts requires skill, patience, and perseverance.
A modifier is a word or phrase that describes (a.k.a. modifies) something. There are two kinds of modifier problems tested on the ACT: dangling modifiers and misplaced modifiers.
A dangling modifier is a modifier that begins a sentence, has a comma after it, and has the noun it describes NOT placed after the comma. In the first example below, for example, the modifier is "coating the sidewalk," and it describes the snow. Since "we" is the first word after the comma, not "snow," "coating the sidewalk" is a dangling modifier. Modifiers are underlined, while nouns being modified are in bold.
Error: Coating the sidewalk, we trudged through the heavy snow.
Corrected: We trudged through the heavy snow coating the sidewalk.
Error: Long and tangled, it was difficult to comb the child's hair.
Corrected: Long and tangled, the child's hair was difficult to comb.
Error: Exhausted and weak, the soldiers' uniforms were covered in frost.
Corrected: Exhausted and weak, the soldiers were covered in frost.
A misplaced modifier is a modifier that's not close enough to the thing it describes, so it looks like it's describing the wrong thing. In the first example below, for example, the modifier "on the sale rack" seems to be describing how the jacket fits the rack, which isn't right. To correct it, we move the modifier closer to the noun it describes.
Error: The jacket was too small on the sale rack.
Corrected: The jacket on the sale rack was too small.
Error: Ray wore his one collared shirt to the job interview, which was stained with mustard.
Corrected: Ray wore his one collared shirt, which was stained with mustard, to the job interview.
Error: She handed out brownies to children wrapped in foil.
Corrected: She handed out brownies wrapped in foil to children.
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We're now going to cover the Rhetorical skills you need for ACT English. Where Usage skills tend to focus on smaller subparts of a sentence, Rhetorical skills broaden the scope to consider how sentences are constructed, and how sentences fit together with each other.
This skill is deciding what the passage is about and whether a certain detail belongs in that category or not. Which sentences, if any, are irrelevant in the paragraph below?
 My uncle explained to me that bonsai cultivation was part of our ancestors’ culture that could remain with me for my whole life.  He said that bonsai as old as Hoshi didn’t need much maintenance, but he would teach me what I needed to know.  He added that I could easily do everything necessary for Hoshi's care in my dorm room.  It’s funny to think that Hoshi is older than my great grandparents. Bonsai are grown from parts of normal-sized trees that are kept small by pruning and planting in small pots.  They thrive in only partial sunlight but need to be pruned several times per year and kept in temperatures that stay well above freezing year-round.  Bonsai also require careful watering, and Hoshi in particular needs to live outside in the summer to get the best light and inside in the winter because of the cold.
If you said Sentence 4 is irrelevant, you're correct. The paragraph is all about bonsai cultivation, and Sentence 4 is about the age of bonsai trees.
For this skill, we need to be able to identify the writer's topic, point, or goal, and the ways she achieves it.
What is the writer's point, t in the above paragraph? The correct answer is something along the lines of "the idea of Ra shows that people personify objects they depend on."
Organization: Transitional Logic
The ACT wants to test our ability to transition between ideas within a sentence, a paragraph, or a whole essay.
Error: All through high school, we were inseparable; however, even our parents eventually became friends.
Corrected: All through high school, we were inseparable; in fact, even our parents eventually became friends.
Error: The painting is a fascinating work because, by representing women in such a novel way, it questions both representational art and traditional notions of femininity. Nonetheless, most critics agree that it is a groundbreaking work in the development of both cubism and modern art as a whole.
Corrected: The painting is a fascinating work because, by representing women in such a novel way, it questions both representational art and traditional notions of femininity. Indeed, most critics agree that it is a groundbreaking work in the development of both cubism and modern art as a whole.
Organization: Macro Logic
Macro-logic is the skill of putting the parts of an essay in the right order. Fortunately, on the ACT, there are tons of clues as to what order sentences and paragraphs should go in. Can you spot the out-of-place sentence(s) in the passage below?
 He wore a sailor’s uniform and used papers given to him by a free black sailor, showed his ingenuity and courage.  After a number of previous failed attempts, Douglass finally escaped to freedom.  He took two boats and two trains to get from Havre de Grace, Maryland to a safehouse in New York City, completing his journey to freedom in less than twenty four hours.  He received the uniform from Anna Murray, a free black woman in Baltimore who later became his wife.
If you said Sentence 4 is out of place, you were right. It should go after Sentence 1.
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Conciseness and Redundancy
There are times when saying something twice is needed: for emphasis, to review a difficult topic, or to explain something more clearly. None of these apply on the ACT. The two ways this skill is tested on the ACT is through wordy sentences and redundant sentences. They're related, but different.
Error: To travel around Berlin, we have the option of choosing many different transport systems; among them are the U-Bahn, or the underground rail system similar to New York’s Subway, and the tram, which is another form of transport that involves railways that have tracks on the streets.
Corrected: To travel around Berlin, we might take the U-Bahn, or subway; we could also take the tram.
Error: High-quality learning environments are a necessary precondition for facilitation and enhancement of the ongoing learning process.
Corrected: Good schools enable people to learn more.
Error: With reference to the fact that the company is deficient in manufacturing and production space, the contract may in all probability be awarded to some other enterprise.
Corrected: The company may not be awarded the contract because it lacks production facilities.
Error: Many uneducated citizens who have never attended school continue to vote for better schools.
Corrected: Many uneducated citizens continue to vote for better schools.
Error: The eye of a storm is a region of mostly calm weather found at the center of a tropical cyclone.
Corrected: The eye is a region of mostly calm weather found at the center of a tropical cyclone.
Error: The teenage woman who wanted to audition was talented, but only sixteen years old.
Corrected: The woman who wanted to audition was talented, but only sixteen years old.
Formality and Tone
Every piece of writing has a level of formality, from none (a note passed in class) to maximum (official government or legal documents). The skill here is understanding the formality of the text (which is always pretty close to a book you'd read in English class). What's the informal phrase in the passage below?
Many cultures in recorded history have venerated and even worshipped the Sun. To some civilizations, the Sun represents all life; to others, the reason for the cycles of day and night. To Plato, the Sun represented the offspring of all that was good. In other myths, though, the Sun might have another kind of significance. It's for sure that the Sun carries great significance for many cultures both ancient and modern.
If you said "it's for sure," you got it! It's less formal than the rest of the passage, which sounds quite academic.
That's every rule tested on the ACT, as well as the ways in which they are likely to appear. Knowing these rules will make it easier to move forward confidently in your ACT practice.
But this is just the beginning. Keep reading to find our most recommended links to master ACT English.
Knowing the grammar rules is just the beginning. Now, you need to practice them over and over again until you perfect your knowledge of them.
Want an 36 on ACT English? Read our detailed guide on how to get a perfect English score. Be sure to also check our ultimate guide to ACT English, with links to all of our articles on ACT English tips and strategies.
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Laura has over a decade of teaching experience at leading universities and scored a perfect score on the SAT.