ACT English: Punctuation Rules — Commas, Semicolons, Apostrophes and Dashes

TL;DR

Mastering commas, semicolons, apostrophes, and dashes is crucial for ACT English, as they dictate sentence structure and meaning. These punctuation marks clarify relationships between words and clauses, helping you identify and correct errors. Knowing the specific rules for each will significantly boost your score.

1. The Mental Model

Think of punctuation as traffic signals for your sentences. Each mark tells your reader how to pause, combine, or separate parts of a sentence, preventing confusion. Understanding these signals helps you build clear, grammatically correct sentences on the ACT.

2. The Core Material

Punctuation isn't just about looking fancy; it's about making your writing clear and precise. The ACT loves to test if you know when and how to use commas, semicolons, apostrophes, and dashes correctly.

Commas (,)

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Commas are the most versatile and frequently tested punctuation mark. You'll primarily use them for:

1. Separating items in a list: "I need to buy milk, eggs, and bread."
2. After an introductory phrase or clause: "Before she left, Sarah locked the door." or "Running quickly, he caught the bus."
3. Setting off non-essential information (appositives, non-restrictive clauses): "My brother, a talented musician, plays the guitar." or "The dog, which was barking loudly, woke everyone up."
4. Before a coordinating conjunction (FANBOYS: For, And, Nor, But, Or, Yet, So) when joining two independent clauses: "He wanted to go, but he was too tired."
5. Separating adjectives that equally describe a noun: "It was a cold, dark night." (If you can swap them or add "and" between them, use a comma).
6. Direct address: "Sarah, please close the door."

Common Comma Traps:
* Comma Splices: Using only a comma to join two independent clauses without a coordinating conjunction. INCORRECT: "I went to the store, I bought groceries." CORRECT: "I went to the store, and I bought groceries." or "I went to the store; I bought groceries."

Semicolons (;)

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Semicolons have two main jobs:

1. Joining two closely related independent clauses without a coordinating conjunction: "The rain fell heavily; the streets were quickly flooded."
2. Separating items in a complex list that already contain commas: "I visited Portland, Oregon; Boise, Idaho; and Seattle, Washington."

Apostrophes (')

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Apostrophes have two main uses:

1. Showing possession:
   • Singular nouns: "The student's book" (one student)
   • Plural nouns ending in -s: "The students' books" (multiple students)
   • Plural nouns not ending in -s: "The children's toys"
   • Possessive pronouns (its, their, your, whose, hers, ours, yours) DO NOT use apostrophes! This is a huge trap!
2. Forming contractions: "It's" (It is), "they're" (they are), "you're" (you are), "don't" (do not).

Apostrophe Trap: Don't confuse "its" (possessive) with "it's" (it is). Don't confuse "their" (possessive) with "they're" (they are) or "there" (place).

Dashes (—)

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Dashes (specifically the em dash, which is a longer dash) are more versatile than hyphens. On the ACT, you'll mainly see them used in pairs or singly:

1. Setting off non-essential information for emphasis or sudden change in thought (similar to parentheses or commas): "The answer—and this surprised everyone—was correct." or "She finally arrived—an hour late, as usual."
2. Introducing a list or explanation: "He brought all the essentials for camping—a tent, a sleeping bag, and a flashlight." (Less common on ACT, but good to know).

When dashes are used in pairs, the information between them is non-essential and could often be removed without changing the sentence's core meaning. Think of them as strong parentheses.

graph TD
    Start["Punctuation Decision"] --> IsolateNonEssential["Isolate non-essential info?"]
    IsolateNonEssential -- Yes --> EmphasisOrAbrupt["For emphasis or abrupt change?"]
    EmphasisOrAbrupt -- Yes --> DashPair["Use Dashes (—info—)"]
    EmphasisOrAbrupt -- No --> LessEmphasis["Less emphasis, more common?"]
    LessEmphasis -- Yes --> CommaPair["Use Commas (,info,)"]
    IsolateNonEssential -- No --> JoinIndependent["Join 2 independent clauses?"]
    JoinIndependent -- Yes --> NoConjunction["No FANBOYS conjunction?"]
    NoConjunction -- Yes --> Semicolon["Use Semicolon (;)"]
    NoConjunction -- No --> ConjunctionUsed["FANBOYS Conjunction used?"]
    ConjunctionUsed -- Yes --> CommaBeforeConjunction["Use Comma before CONJUNCTION (, FANBOYS)"]
    JoinIndependent -- No --> ListItems["Separate items in a list?"]
    ListItems -- Yes --> ComplexItems["Items already contain commas?"]
    ComplexItems -- Yes --> SemicolonList["Use Semicolons (item1; item2; item3)"]
    ComplexItems -- No --> CommaList["Use Commas (item1, item2, item3)"]
    ListItems -- No --> ShowPossession["Show possession or contraction?"]
    ShowPossession -- Yes --> PossessiveOrContraction["Use Apostrophe (')"]
    ShowPossession -- No --> OtherRules["Other comma rules (intro, adj, direct address)"]
    OtherRules -- Apply --> Comma["Use Comma (,)"]
    CommaPair --> End
    CommaBeforeConjunction --> End
    Semicolon --> End
    SemicolonList --> End
    CommaList --> End
    PossessiveOrContraction --> End
    DashPair --> End
    Comma --> End

3. Worked Example

Let's look at a sentence and identify necessary punctuation:

"Although she was tired Sarah a diligent student finished her homework before starting to read the challenging novel it had been recommended by her English teacher."

Here's how we'd fix it:

"Although she was tired, Sarah, a diligent student, finished her homework before starting to read the challenging novel; it had been recommended by her English teacher."

• Comma after "tired": This separates the introductory dependent clause "Although she was tired" from the independent clause.
• Commas around "a diligent student": This phrase is an appositive, providing non-essential information about Sarah. It can be removed without changing the core sentence meaning.
• Semicolon after "novel": We have two closely related independent clauses ("Sarah...finished her homework" and "it had been recommended..."). A semicolon correctly joins them without a coordinating conjunction.

4. Key Takeaways

• Use commas to separate items in lists, after introductory elements, and around non-essential information.
• Never use a single comma to join two independent clauses; that's a comma splice.
• Use semicolons to join two independent clauses or separate complex list items that already contain commas.
• Apostrophes indicate possession or form contractions; avoid using them for possessive pronouns like "its" or "theirs."
• Dashes (or pairs of dashes) set off information for emphasis or abrupt changes, similar to parentheses.

Common Mistakes to Avoid:
- Comma Splices: Don't join two complete sentences with just a comma.
- "Its" vs. "It's": Remember "its" is possessive, "it's" means "it is."
- Missing Commas around Non-Essential Phrases: Ensure you're properly setting off extra details.
- Overusing Semicolons: Only use them when appropriate, not just to sound fancy.

5. Now Try It

Review 5-10 sentences from a practice ACT English passage. For each sentence, identify every comma, semicolon, apostrophe, or dash. Explain why each piece of punctuation is used according to the rules above, or if it's used incorrectly, explain the error and how to fix it. Success means you can correctly identify and justify at least 80% of the punctuation marks.