Punctuation questions are among the most frequently tested topics on the ACT English section. Of the 75 questions you'll face in 45 minutes, roughly 10–15 will directly test your knowledge of commas, semicolons, colons, and dashes. The good news? Punctuation rules are concrete and learnable — unlike some rhetoric questions that require subjective judgment, punctuation has clear right and wrong answers.
The ACT English section presents five passages, each accompanied by 15 questions. Many questions highlight an underlined portion of the passage and ask you to choose the best alternative. For punctuation questions, the answer choices often differ only in the placement or type of punctuation mark used. This means you need to know the specific rules governing each mark — guessing based on "what sounds right" will lead you astray.
This guide covers the four major punctuation marks tested on the ACT: commas, semicolons, colons, and dashes. You'll learn the precise rules for each, see worked examples modeled on ACT-style questions, and practice applying these rules under test-like conditions. By the end, you'll be able to spot punctuation errors quickly and confidently — a crucial skill when you have only 36 seconds per question.
Core Concepts
Comma Rules
Commas are the most heavily tested punctuation mark on the ACT. Here are the essential comma rules you must know:
1. Commas with FANBOYS (Coordinating Conjunctions)
When joining two independent clauses (complete sentences) with a coordinating conjunction — For, And, Nor, But, Or, Yet, So — place a comma before the conjunction.
- Correct: The experiment took three weeks, and the results surprised the entire team.
- Incorrect: The experiment took three weeks and the results surprised the entire team.
Critical distinction: Do NOT use a comma before FANBOYS when the second part is not an independent clause.
- Correct: She studied hard and earned a perfect score. ("earned a perfect score" is not an independent clause — no subject)
- Incorrect: She studied hard, and earned a perfect score.
2. Commas After Introductory Elements
Place a comma after introductory words, phrases, or clauses that come before the main clause.
- After introductory clauses: When the bell rang, the students rushed to the door.
- After introductory phrases: In the middle of the night, the phone began to ring.
- After introductory words: However, the data did not support the hypothesis.
3. Commas with Appositives and Nonessential Information
Use commas to set off nonessential (nonrestrictive) information — details that can be removed without changing the sentence's core meaning.
- Dr. Martinez, a leading researcher in marine biology, published her findings last month.
- The painting, which was completed in 1889, hangs in a museum in Paris.
Do NOT use commas with essential (restrictive) information — details necessary to identify the noun.
- The student who scored highest received a scholarship. (No commas — "who scored highest" is essential to identify which student)
4. Commas in Lists (Serial Comma)
Use commas to separate three or more items in a series. The ACT accepts the Oxford comma (comma before "and" in a list).
- The recipe calls for flour, sugar, butter, and eggs.
5. Commas Between Adjectives
Use a comma between coordinate adjectives (adjectives that independently modify the noun). Test by inserting "and" between them — if it sounds natural, use a comma.
- She gave a long, passionate speech. ("long and passionate" works → comma needed)
- She wore a bright red dress. ("bright and red" sounds wrong → no comma)
Semicolon Rules
Semicolons appear less frequently than commas on the ACT but are tested consistently. There are only two main uses:
1. Joining Two Independent Clauses Without a Conjunction
A semicolon can replace a period between two closely related independent clauses.
- Correct: The trail was steep; many hikers turned back before reaching the summit.
- Incorrect: The trail was steep; and many hikers turned back. (Don't combine semicolons with FANBOYS)
2. Semicolons with Conjunctive Adverbs
When a conjunctive adverb (however, therefore, moreover, nevertheless, furthermore, consequently) connects two independent clauses, use a semicolon before and a comma after the adverb.
- Correct: The data was inconclusive; however, the team decided to publish their preliminary findings.
- Incorrect: The data was inconclusive, however, the team decided to publish. (This creates a comma splice)
3. Semicolons in Complex Lists
Use semicolons to separate items in a list when the items themselves contain commas.
- The tour visited Paris, France; Rome, Italy; and Tokyo, Japan.
Colon Rules
Colons have a simple but strict rule on the ACT:
The clause before a colon must be an independent clause (a complete sentence). What follows can be a list, an explanation, or an elaboration.
- Correct: She packed three things: a tent, a sleeping bag, and a flashlight.
- Incorrect: She packed: a tent, a sleeping bag, and a flashlight. ("She packed" is not a complete sentence in this context — it needs an object)
Common ACT trap: Using a colon after "such as" or "including."
- Incorrect: Fruits such as: apples, oranges, and bananas.
- Correct: Fruits such as apples, oranges, and bananas.
Dash Rules
Dashes (em dashes) function similarly to commas or parentheses for setting off nonessential information, but they add emphasis.
Key ACT Rule: Dashes must come in pairs when used mid-sentence (unless the set-off information ends the sentence).
- Correct: The politician — known for her fiery speeches — addressed the crowd.
- Correct: There was only one option left — retreat.
- Incorrect: The politician — known for her fiery speeches, addressed the crowd. (Can't mix dash and comma)
The ACT frequently tests whether students can maintain consistency: if a dash opens a parenthetical aside, a dash must close it.
Strategy Tips
Tip 1: Read the Whole Sentence Before Choosing
Don't just look at the underlined portion. Punctuation depends on the grammatical structure of the entire sentence. Read from the beginning of the sentence to its end before selecting your answer.
Tip 2: Identify the Clause Structure First
Before deciding on punctuation, determine whether you're looking at one independent clause, two independent clauses, or a dependent clause paired with an independent clause. This single step eliminates most wrong answers.
Tip 3: Watch for "NO CHANGE"
On the ACT, the first answer choice (A or F) is always "NO CHANGE." Approximately 25% of answers are NO CHANGE, so don't be afraid to select it — but don't default to it either.
Tip 4: When in Doubt, Choose the Least Punctuation
The ACT generally favors the simplest correct option. If you're torn between two choices and both seem grammatically defensible, the one with less punctuation is usually correct. Unnecessary commas are a common trap.
Tip 5: Match Pairs
If you see one dash, look for a matching dash. If you see a comma opening a nonessential clause, look for the closing comma. Mismatched pairs are always wrong on the ACT.
Worked Example: Example 1
The orchestra, which had been rehearsing for months _____ performed flawlessly on opening night.
(A) months, (B) months; (C) months (D) months —
The phrase "which had been rehearsing for months" is a nonessential clause set off by a comma after "orchestra." Since the opening punctuation is a comma, the closing punctuation must also be a comma to create a matching pair. Choice (A) is correct. A semicolon (B) cannot appear mid-clause. Removing punctuation (C) breaks the nonessential clause structure. A dash (D) would need a matching dash at the opening. Answer: (A)
Worked Example: Example 2
Marcus wanted to visit three cities on his European trip _____ London, Barcelona, and Prague.
(F) trip; (G) trip: (H) trip, (J) trip
The sentence introduces a list of cities. A colon is appropriate here because "Marcus wanted to visit three cities on his European trip" is a complete independent clause, and the list elaborates on "three cities." A semicolon (F) would require an independent clause to follow. A comma (H) is too weak for introducing a list in this structure. No punctuation (J) creates a run-on. Answer: (G)
Worked Example: Example 3
The new policy reduced emissions by 30 percent _____ it also created thousands of green jobs.
(A) percent, it (B) percent; it (C) percent it (D) percent, and, it
Both parts are independent clauses. Choice (A) creates a comma splice — two independent clauses joined only by a comma. Choice (C) is a fused sentence (run-on). Choice (D) has an unnecessary comma after "and." A semicolon correctly joins two independent clauses without a conjunction. Answer: (B)
Worked Example: Example 4
Dr. Patel — the department's most published researcher _____ was nominated for the university's highest honor.
(F) researcher, (G) researcher — (H) researcher; (J) researcher
The nonessential information "the department's most published researcher" is opened with a dash. Consistency requires it to close with a dash as well. Mixing a dash with a comma (F) is incorrect. A semicolon (H) cannot close a parenthetical. Dropping punctuation (J) leaves the parenthetical unmarked. Answer: (G)
Worked Example: Example 5
After reviewing the evidence _____ the jury reached a unanimous verdict.
(A) evidence; the (B) evidence, the (C) evidence: the (D) evidence the
"After reviewing the evidence" is an introductory dependent clause. A comma should follow an introductory clause before the main clause. A semicolon (A) requires two independent clauses. A colon (C) requires an independent clause before it. No punctuation (D) ignores the introductory element rule. Answer: (B)
Practice Problems
Problem 1
The artist known for her vivid landscapes _____ recently opened a gallery in downtown Portland.
(A) landscapes, (B) landscapes; (C) landscapes (D) landscapes:
Problem 2
Swimming is excellent cardiovascular exercise _____ however, it requires access to a pool.
(F) exercise, (G) exercise; (H) exercise: (J) exercise
Problem 3
The committee proposed several changes _____ longer lunch periods, flexible start times, and reduced homework loads.
(A) changes; (B) changes: (C) changes, (D) changes —
Problem 4
Before the concert began _____ the lead singer addressed the audience with a heartfelt speech about community service.
(F) began; (G) began (H) began, (J) began:
Problem 5
The novel — praised by critics and readers alike _____ became the bestselling book of the year.
(A) alike, (B) alike; (C) alike — (D) alike
Answers: 1. (C) — "known for her vivid landscapes" is essential information (identifies which artist), so no commas. 2. (G) — "however" is a conjunctive adverb joining two independent clauses; use semicolon before, comma after. 3. (B) — The clause before the list is independent, and a colon introduces the list. 4. (H) — "Before the concert began" is an introductory dependent clause; use a comma. 5. (C) — A dash opened the nonessential phrase, so a dash must close it.
Want to check your answers and get step-by-step solutions?
Common Mistakes
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Comma splices. Joining two complete sentences with just a comma is the most common punctuation error on the ACT. If you see two independent clauses separated by a comma alone, it's wrong — you need a semicolon, a period, or a comma plus FANBOYS.
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Unnecessary commas. Many students add commas wherever they would "pause" when reading aloud. The ACT tests grammar rules, not pauses. Never place a comma between a subject and its verb or between a verb and its direct object.
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Mixing punctuation pairs. If a nonessential phrase opens with a dash, it must close with a dash. If it opens with a comma, it must close with a comma. The ACT loves testing mismatched pairs like "dash ... comma."
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Colon after an incomplete clause. A colon must follow a complete sentence. Students frequently choose colons after phrases like "such as" or "including," which don't form independent clauses.
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Semicolon before a dependent clause. Semicolons connect two independent clauses. Using a semicolon before "which," "because," or "although" is always wrong on the ACT.
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Forgetting commas after introductory elements. Short introductory phrases sometimes seem like they don't need commas, but the ACT consistently requires them after introductory dependent clauses and longer prepositional phrases.
Frequently Asked Questions
How many punctuation questions are on the ACT English section?
While the exact number varies by test, you can expect 10–15 questions (out of 75) to focus primarily on punctuation. This makes it one of the highest-yield topics to study. Punctuation questions also tend to be among the most straightforward once you know the rules.
Is the Oxford comma required on the ACT?
The ACT consistently uses and expects the Oxford comma (the comma before "and" in a series of three or more items). In list-based questions, the correct answer will include the serial comma.
How can I tell the difference between essential and nonessential clauses?
Ask yourself: "If I remove this clause, does the sentence still make sense AND still refer to the same specific thing?" If the clause is just extra detail (nonessential), use commas. If removing it changes which person or thing you're talking about (essential), don't use commas. On the ACT, "which" typically introduces nonessential clauses (with commas), while "that" introduces essential clauses (no commas).
Can I use a semicolon before "and" or "but"?
Generally, no. On the ACT, a semicolon should not be combined with a coordinating conjunction (FANBOYS). Use either a semicolon alone or a comma plus a coordinating conjunction — not both. The exception is in complex lists where items contain internal commas.
What's the difference between a dash and a comma for setting off information?
Both can set off nonessential information, but dashes add emphasis and are more informal. On the ACT, the key rule is consistency: if the nonessential phrase starts with a dash, it must end with a dash. You cannot mix dashes with commas. When an answer choice pairs a dash with a comma, it's wrong.
Key Takeaways
Master the comma splice rule. Two independent clauses cannot be joined by a comma alone — use a semicolon, a period, or a comma with a FANBOYS conjunction. This is the single most tested punctuation concept on the ACT.
Know your clause types. Identifying independent vs. dependent clauses is the foundation for nearly every punctuation question. If you can spot clause boundaries, you can apply the correct punctuation rule.
Colons require a complete sentence before them. Whatever comes before a colon must be able to stand alone as a sentence. If it can't, the colon is wrong.
Match your pairs. Dashes pair with dashes, commas pair with commas. Mismatched punctuation around nonessential information is always incorrect.
Less is often more. When you're unsure, lean toward fewer commas. The ACT penalizes unnecessary punctuation more often than missing punctuation.
Use the 36-second rule wisely. Punctuation questions are usually quick wins. Identify the structure, apply the rule, and move on — save your time for harder rhetoric questions.
Semicolons are for independent clauses. If what follows a semicolon couldn't stand alone as a sentence (unless it's part of a complex list), the semicolon is wrong.