The Grammar Foundations Behind Every High ACT English Score

The Foundations of English Grammar

Understanding the Eight Parts of Speech

To build strong sentences, you must first understand the components that make them work. English grammar is based on eight fundamental parts of speech. Each plays a unique role in sentence construction, and understanding how these elements interact helps improve clarity and correctness.

Nouns

A noun is a word used to name a person, place, thing, or idea. Nouns can be concrete (cat, city, book) or abstract (freedom, truth, anger). They often serve as the subject or object in a sentence.

Examples:

• The dog barked loudly.

• Happiness is a choice.

Pronouns

Pronouns replace nouns to avoid repetition. Common types include:

• Personal pronouns: I, you, he, she, it, we, they

• Possessive pronouns: my, your, his, her, its, our, their

• Reflexive pronouns: myself, yourself, themselves

Examples:

• She gave her notes to him.

• I made this decision myself.

Pronoun clarity and agreement are frequently tested on the ACT.

Verbs

Verbs express actions, conditions, or states of being. There are several kinds:

• Action verbs: run, think, discover

• Linking verbs: be, seem, become

• Helping verbs: is, has, will (used with other verbs to show tense or mood)

Examples:

• He runs every morning.

• She is happy.

• They have been studying all day.

Verbs are central to every sentence, and their correct form must match

Sentence Structure and Sentence Boundaries

What Makes a Sentence Complete?

At its core, a complete sentence in English must contain two essential components:

• A subject: who or what the sentence is about.

• A predicate: what the subject is doing or what is being said about the subject.

Additionally, the sentence must express a complete thought. If any of these elements are missing, the sentence becomes a fragment.

Example of a complete sentence:

• The students (subject) finished their exams (predicate).

This sentence has both a subject and a predicate and expresses a complete idea.

Sentence Fragments

A sentence fragment is an incomplete sentence that is punctuated as if it were complete. Fragments often occur because a subject or a verb is missing, or because the group of words is a dependent clause that cannot stand alone.

Examples:

• Because the rain was falling. (incomplete — dependent clause)

• Running through the park. (incomplete — no subject or main verb)

Corrected versions:

• Because the rain was falling, we stayed indoors.

• She was running through the park when she saw the deer.

On the ACT, fragments are tested frequently, especially when dependent clauses are mistakenly punctuated as full sentences.

Run-On Sentences

A run-on sentence occurs when two or more independent clauses are joined incorrectly. This usually happens when there is no punctuation or when only a comma is used without a coordinating conjunction.

Example of a run-on:

• He studied all night; he didn’t take any breaks.

There are several ways to fix a run-on:

1. Use a period to create two separate sentences:
   • He studied all night. He didn’t take any breaks.

2. Use a semicolon if the ideas are closely related:
   • He studied all night; he didn’t take any breaks.

3. Use a comma and d coordinating conjunction:
   • He studied all night, and he didn’t take any breaks.

The ACT often tests the ability to recognize and correct run-ons using these methods.

Comma Splices

A comma splice is a type of run-on sentence where two independent clauses are incorrectly joined by just a comma.

Example:

• The sun was setting, the sky turned pink.

Corrections:

• The sun was setting. The sky turned pink.

• The sun was setting, and the sky turned pink.

• The sun was setting; the sky turned pink.

Comma splices are easy to miss because the sentence may sound natural when read aloud, so it’s essential to check whether each clause could stand on its own.

Coordination and Subordination

Understanding how to join ideas within a sentence is key to effective writing. Sentences can be structured with coordination or subordination to show the relationship between thoughts.

Coordination

Coordination connects two or more ideas of equal importance. Coordinating conjunctions include: for, and, nor, but, or, yet, so (often remembered with the acronym FANBOYS).

Example:

• I wanted to go to the game, but I had too much homework.

Here, both clauses are independent and joined by a comma and a coordinating conjunction.

Subordination

Subordination makes one idea dependent on another by using subordinating conjunctions like: although, because, since, unless, while, if, when.

Example:

• Although I wanted to go to the game, I had too much homework.

This sentence uses a dependent clause (Although I wanted to go to the game) to explain the main clause (I had too much homework).

On the ACT, choosing between coordination and subordination is tested for both grammar and rhetorical clarity.

Sentence Types: Simple, Compound, Complex, and Compound-Complex

Understanding how sentence elements combine to form different structures is essential for sentence variety and clarity. Here are the four main sentence types:

Simple Sentences

A simple sentence contains one independent clause.

Example:

• The cat slept on the windowsill.

Even though it’s simple, this sentence is complete and grammatically correct.

Compound Sentences

A compound sentence contains two or more independent clauses joined by a coordinating conjunction or a semicolon.

Examples:

• I cooked dinner, and she washed the dishes.

• I wanted to read; however, I fell asleep.

Each clause could stand alone, and the connection shows how the ideas relate.

Complex Sentences

A complex sentence contains one independent clause and at least one dependent clause.

Example:

• Because it was raining, we canceled the picnic.

The dependent clause “Because it was raining” explains the main clause and cannot stand alone.

Compound-Complex Sentences

A compound-complex sentence contains at least two independent clauses and one or more dependent clauses.

Example:

• Although it was late, I kept working, and my friend made coffee.

This sentence contains a dependent clause (“Although it was late”) and two independent clauses (“I kept working” and “my friend made coffee”).

The ACT’s recognition and revision of all four sentence types.

Parallel Structure

Parallel structure means using the same grammatical form for elements that appear in a list or series. This creates balance and clarity in writing.

Incorrect:

• She enjoys hiking, swimming, and biking.

Correct:

• She enjoys hiking, swimming, and biking.

All the items in the list are in the gerund form (-ing), making the sentence easier to read and more professional.

Parallel structure is also important in comparisons and paired ideas:

Incorrect:

• He wanted not only to win the match but also to gain respect.

Correct:

• He wanted not only to win the match but also to gain respect.

On the ACT, you may be asked to revise sentences for consistency in structure.

Modifier Placement and Clarity

Modifiers add description to sentences, but they must be placed next to the word they are meant to modify. When misplaced, they confuse or create unintentional meanings.

Misplaced Modifiers

Example:

• Incorrect: She served sandwiches to the children on paper plates.

• Correct: She served the children sandwiches on paper plates.

In the incorrect version, it sounds like the children are on the plates.

Dangling Modifiers

A dangling modifier is a descriptive phrase that lacks a clear subject.

Example:

• Incorrect: Walking through the woods, the birds chirped loudly.

• Correct: Walking through the woods, I heard the birds chirping loudly.

The corrected version clarifies who was walking through the woods.

Both misplaced and dangling modifiers are common ACT errors.

Verb Tense Consistency

Verbs should remain consistent in tense unless there is a clear shift in the timeline.

Incorrect:

• She woke up, got dressed, and left the house.

Correct:

• She woke up, got dressed, and left the house.

The ACT will test whether you can identify and correct unnecessary shifts in verb tense, especially in narrative or explanatory passages.

Punctuation Rules and Usage

Punctuation is essential in written English because it helps clarify meaning, indicate structure, and guide the reader through sentences. The ACT English section frequently tests the correct use of punctuation marks, especially within compound and complex sentence structures. Understanding how and when to use each punctuation mark is key to performing well on the test.

End Punctuation

End punctuation indicates the conclusion of a sentence and helps define the sentence’s purpose.

Period (.)

A period is used at the end of a declarative sentence, which makes a statement.

Example:

• The students completed the exam.

Question Mark (?)

A question mark is used at the end of an interrogative sentence, which asks a question.

Example:

• Did the students complete the exam?

Exclamation Point (!)

An exclamation point is used at the end of an exclamatory sentence, which expresses strong emotion.

Example:

• The students finished just in time!

While periods are the most common end punctuation, the ACT may test the ability to distinguish between statements and questions or spot inappropriate exclamation points.

Commas

The comma is one of the most versatile and commonly misused punctuation marks. On the ACT, you’ll often encounter questions that require knowing when to use — or not use — a comma.

1. Commas in Compound Sentences

When joining two independent clauses with a coordinating conjunction (for, and, nor, but, or, yet, so), place a comma before the conjunction.

Correct:

• I wanted to go to the movie, but I had too much homework.

Incorrect:

• I wanted to go to the movie, but I had too much homework.

However, do not use a comma if the second part is not an independent clause:

Incorrect:

• I wanted to go, but I had too much homework.

Correct:

• I wanted to go but had too much homework.

2. Commas After Introductory Elements

Use a comma after introductory words, phrases, or clauses.

Examples:

• After the game, we went out for dinner.

• Yes, I understand your point.

• While I was reading, the phone rang.

This rule is especially common with introductory dependent clauses in complex sentences.

3. Commas with Lists

Use commas to separate three or more items in a list. The ACT accepts both the Oxford comma (comma before “and”) and omitting it, but consistency matters.

Examples:

• We bought apples, oranges, and bananas.

• She enjoys painting, singing, dancing, and hiking.

Be cautious of misplaced commas when two items are connected by “and”:

Incorrect:

• He packed socks and shoes.
  Correct:

• He packed socks and shoes.

4. Commas to Set Off Nonessential Information

Use commas to set off nonessential clauses or phrases—information that can be removed without changing the sentence’s basic meaning.

Example:

• My brother, who lives in Chicago, is visiting us next week.

Here, “who lives in Chicago” is not essential to the main idea of the sentence. If the information is essential, no commas should be used.

Essential:

• People who live in Chicago often deal with snow in winter.

The ACT frequently tests whether a clause is essential or nonessential to the sentence.

Semicolons

A semicolon connects two closely related independent clauses that could stand alone as sentences but are more effective when linked.

Correct:

• I studied all night; I still felt unprepared.

Using a semicolon in place of a comma without a coordinating conjunction is a common fix for comma splices.

A semicolon can also be used before a conjunctive adverb (such as however, therefore, moreover, consequently) when joining two independent clauses:

Example:

• I was tired; however, I kept working.

Incorrect:

• I was tired, but I kept working. (comma splice)

Be sure to follow the conjunctive adverb with a comma.

Correct:

• She loves to travel; therefore, she saves money regularly.

Colons

A colon introduces information that follows logically from the clause that precedes it. The clause before the colon must be independent.

Use colons to introduce:

• A list

• A quotation

• An explanation or elaboration

Examples:

• He brought three things to the picnic: sandwiches, drinks, and fruit.

• She had one rule: never give up.

Do not use a colon immediately after a verb or preposition unless the sentence before it is a complete thought.

Incorrect:

• His favorite hobbies are reading, hiking, and cooking.
  Correct:

• He has three favorite hobbies: reading, hiking, and cooking.

Colons are often confused with semicolons, so be sure you understand the difference.

Apostrophes

Apostrophes are used in two main ways:

1. To Show Possession

• Singular possessive: The dog’s leash

• Plural possessive: The students’ books

• Plural nouns not ending in “s”: The children’s toys.

Be careful not to confuse plurals with possessives.

Incorrect: The teacher’s classroom was quiet.
Correct: The teacher’s classroom was quiet.

2. In Contractions

Apostrophes replace omitted letters in contractions:

• Can’t = cannot

• They’re = they are

• It’s = it is

A common error on the ACT is confusing its (possessive) with it’s (contraction for “it is”).

Examples:

• It’s going to rain. (it is)

• The cat licked its paw. (possessive)

Quotation Marks

Quotation marks are used to enclose direct speech or a quotation from another source.

Examples:

• He said, “I will be late.”

• “Honesty is the best policy,” she replied.

When punctuating dialogue, place commas and periods inside the closing quotation mark in American English:

Correct:

• “I’m leaving,” she said.

Also, capitalize the first word of a complete sentence inside quotation marks.

Incorrect:

• She said, “Do your best.”
  Correct:

• She said, “Do your best.”

Quotation marks are rarely tested on the ACT, but you may encounter questions that involve quotation marks within sentence correction or rhetorical skills passages.

Parentheses and Dashes

Parentheses ( )

Parentheses enclose information that is not essential to the main point. This information is often explanatory or additional detail.

Example:

• She moved to San Diego (a city she had never visited) for her new job.

This information could be removed without changing the main idea of the sentence.

Dashes (—)

Dashes are versatile and often used for emphasis, interruptions, or appositives that contain internal commas. A dash is more dramatic than a comma or parentheses and often draws attention to the inserted material.

Examples:

• Everything he said — every single word — was a lie.

• She had one goal — to win the championship.

Dashes must appear in pairs when used within a sentence to enclose material (like parentheses).

Incorrect:

• My sister, who lives in New York, is visiting.
  Correct:

• My sister, who lives in New York, is visiting.

The ACT may test the consistency of punctuation marks, choosing between commas, dashes, or parentheses. Only one form should be used to set off interrupting material.

Hyphens

Hyphens are used within compound modifiers before a noun or to form certain compound words.

Examples:

• A well-written essay

• A high-speed chase

However, if the compound modifier comes after the noun, the hyphen is often not needed.

Example:

• The essay was well written.

Hyphen use is less commonly tested on the ACT but can still appear in questions involving compound adjectives.

Word Usage and ACT Strategy

The ACT English section does not only grammar, punctuation, and sentence structure. It also evaluates your understanding of word usage and your ability to recognize concise, logical, and effective word choices. Additionally, mastering strategic approaches to this section is essential for improving your score. This part will focus on correct word usage, commonly confused words, idiomatic expressions, and test-day strategies.

Word Choice and Usage

Choosing the right word is not only a matter of grammar—it also affects the tone, precision, and clarity of your writing. On the ACT, you’ll be tested on whether a word fits in context, both grammatically and logically.

1. Commonly Confused Words

The ACT frequently includes questions that test your ability to distinguish between words that sound or look similar but have different meanings or uses.

Homophones are a common focus. These are words that sound alike but have different spellings and meanings.

Examples:

• Their (possessive pronoun): Their house is beautiful.

• There (adverb indicating place): The keys are over there.

• They’re (contraction of they are): They’re going to the party.

• Your (possessive pronoun): Your coat is on the chair.

• You’re (contraction of you are): You’re going to love this movie.
  It’s (possessive): The dog wagged its tail.

• It’s (contraction): It’s going to rain today.

ACT questions may simply ask you to choose the correct word or may include it within a sentence where the incorrect word changes the meaning entirely.

2. Words with Similar Spellings

The ACT sometimes includes words that look alike but are used differently.

Examples:

• Accept (verb): to receive
  • I accept your apology.

• Except (preposition): excluding
  • Everyone went except Jake.

• Affect (verb): to influence
  • The weather can affect your mood.

• Effect (noun): a result
  • The medicine had side effects.

Knowing the part of speech required by the sentence will help you choose the correct word.

3. Common Usage Errors

Some word usage questions are not about confusing words but about proper idiomatic expressions, word forms, or prepositions.

Examples:

• Incorrect: She is capable of succeeding.

• Correct: She is capable of succeeding.

• Incorrect: He is interested in.

• Correct: He is interested in art.

Another example involves redundant or informal phrases:

• Incorrect: I think that it is unnecessary.

• Correct: I think it is unnecessary.

The ACT favors clear, concise, and formal word choices. Unnecessary modifiers like “personally,” “basically,” or “really” often weaken writing and should be removed.

Wordiness and Redundancy

One of the most commonly tested rhetorical skills on the ACT is conciseness. You may be asked to choose between several options that say the same thing, and your job is to select the most concise and clear version.

Redundancy means repeating the same idea unnecessarily:

• Incorrect: The reason why he left was that he was tired.

• Correct: He left because he was tired.

• Incorrect: She concluded at the end.

• Correct: She concluded.

The ACT often includes wordy options among the answer choices, and the best answer is usually the one that removes redundancy while maintaining the sentence’s meaning.

Idiomatic Expressions

An idiom is a phrase or construction that follows a particular pattern in English usage. These expressions may not make sense if translated word for word into another language, which is why they can be tricky even for native speakers.

Examples:

• Wrong: He succeeded in winning the prize.

• Right: He succeeded in winning the prize.

• Wrong: She is responsible for organizing the meeting.

• Right: She is responsible for organizing the meeting.

Idioms can involve prepositions, verb patterns, or fixed expressions. The ACTs our understanding of what “sounds right” according to standard usage.

Comparative and Superlative Forms

When comparing two things, use the comparative form; when comparing three or more, use the superlative.

Examples:

• Comparative: She is taller than her brother.

• Superlative: She is the tallest person in the room.

Incorrect usage often involves mixing up these forms:

• Wrong: Of the two, he is the fastest.

• Right: Of the two, he is the faster.

• Wrong: This is the most fun game of all.

• Right: This is the most fun game of all.

Knowing when and how to compare correctly is another frequently tested rule.

Clarity and Precision

Besides choosing grammatically correct words, you must also aim for precise word choice. The ACT often tests vague language versus specific, descriptive terms.

Example:

• Vague: He had a thing on his desk.

• Precise: He had a document on his desk.

Precision helps improve the reader’s understanding. Avoid vague nouns (thing, stuff, way) and use vocabulary that reflects your meaning.

ACT English Section Strategies

Now that you understand the grammar content, mastering the ACT English section also depends on your ability to apply strategies under timed conditions.

1. Read the Entire Sentence

Even though questions are underlined individually, always read the entire sentence before making a choice. Context is crucial for identifying subject-verb agreement, pronoun clarity, and modifier placement.

2. Plug in the Answers

Often, the best way to check which option works is to mentally plug each one into the sentence. Eliminate choices that introduce errors, change meaning, or sound awkward.

3. Favor Simplicity and Clarity

The ACT almost always prefers concise and direct answers. If two choices seem grammatically correct, pick the one that is shorter and more straightforward unless the longer option is more precise or informative.

4. Watch Out for “No Change”

The first answer choice on ACT English questions is always “No Change.” While it’s correct about 25% of the time, don’t choose it unless you are confident the sentence is already correct.

5. Look for Patterns

When several questions appear in a row about sentence structure or punctuation, look for patterns: Is a particular clause consistently missing a subject? Is a semicolon being misused in multiple places?

Identifying these patterns helps answer multiple questions at once.

6. Pace Yourself

There are 75 questions and only 45 minutes on the ACT English section. That gives you less than a minute per question. Don’t get stuck on a difficult item. Move on and return later if time permits.

7. Don’t Overthink It

Many errors are straightforward, and many correct sentences are short and simple. Avoid trying to impose complex grammatical rules where they don’t belong.

8. Trust Your Ear—but Know the Rules

While your instincts can help, they must be grounded in real grammar rules. If something “sounds wrong,” analyze why it’s wrong using the grammatical concepts covered here.

Practice and Review

Regular practice is the most effective way to improve on the ACT English section. Focus your review on the following high-yield topics:

• Subject-verb agreement

• Pronoun clarity and agreement

• Punctuation (especially commas and semicolons)

• Sentence structure (avoiding run-ons and fragments)

• Word usage and idiomatic expressions

• Conciseness and redundancy

• Modifier placement

• Logical transitions between ideas

When you review practice tests, analyze every wrong answer: not just what the correct answer is, but why your answer was incorrect. Over time, you’ll develop a sense for the most common traps and how to avoid them.

Final Thoughts

Mastering the ACT English section comes down to understanding and applying the core principles of grammar, punctuation, sentence structure, and word usage. Rather than testing obscure rules, the section focuses on clarity, conciseness, and consistency in standard written English. Success depends on your ability to recognize common errors—like subject-verb disagreement, misplaced modifiers, or incorrect punctuation—and revise them effectively. Strong performance also requires reading for context, not just isolated phrases, and identifying how each part of a sentence or passage contributes to the overall meaning. With focused practice, attention to detail, and smart time management, you can approach each question with confidence and precision, improving both your accuracy and your efficiency.