Punctuation Rules

Why This Matters

Punctuation isn't just about following rules—it's about controlling how your reader experiences your writing. On the PSAT and in English 10, you're being tested on whether you understand that punctuation marks are traffic signals for sentences: they tell readers when to pause, stop, or shift gears. Every comma splice you fix and every semicolon you deploy correctly demonstrates your command of sentence structure, which is the foundation of clear, persuasive writing.

The key concepts here are sentence boundaries, clause relationships, and ownership signals. When you see a punctuation question on a standardized test, the real question is usually: "Do you know where one idea ends and another begins?" Don't just memorize which mark goes where—understand why each punctuation mark exists and what grammatical problem it solves. That's what separates students who guess from students who know.

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Marks That End and Separate Sentences

These punctuation marks establish the most fundamental boundaries in writing: where one complete thought stops and another begins. Mastering these means you'll never write a run-on or fragment again.

End Punctuation (Periods, Question Marks, Exclamation Points)

• Periods signal a complete declarative statement—the default ending for most sentences you'll write
• Question marks indicate interrogative sentences and must match the sentence's grammatical structure, not just its tone
• Exclamation points express strong emotion but should be used sparingly in formal writing—overuse weakens their impact

Semicolons to Join Independent Clauses

• Semicolons connect two independent clauses without a conjunction—both sides must be complete sentences
• Use semicolons for closely related ideas where a period would feel too abrupt and a comma would be incorrect
• Complex lists with internal commas require semicolons as separators to prevent confusion

Colons for Introducing Lists or Explanations

• Colons follow independent clauses and introduce what comes next—a list, explanation, or elaboration
• Never place a colon after a verb or preposition—the clause before the colon must stand alone
• Colons create anticipation—they signal to readers that important information is about to follow

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Marks That Join and Separate Within Sentences

Commas are the most frequently tested—and most frequently misused—punctuation marks. Understanding their specific jobs prevents the dreaded comma splice and the awkward missing comma.

Commas in Compound Sentences

• Use a comma before FANBOYS (for, and, nor, but, or, yet, so) when joining two independent clauses
• Both clauses must be complete sentences—if you remove the conjunction, each side should stand alone
• No comma needed if the second part isn't an independent clause (just a phrase or dependent clause)

Commas for Separating Items in a List

• Three or more items require commas between each element in a series
• The Oxford comma (before the final conjunction) prevents ambiguity—"I love my parents, Batman, and Wonder Woman" vs. "I love my parents, Batman and Wonder Woman"
• Consistency matters—pick a style and stick with it throughout your writing

Punctuation with Dialogue

• Commas separate dialogue from speaker tags—"She whispered, 'Follow me'" or "'Follow me,' she whispered"
• New paragraph for each new speaker—this convention helps readers track who's talking
• Punctuation stays inside quotation marks in American English—periods, commas, question marks all go before the closing quote

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Marks That Show Ownership and Omission

These punctuation marks modify words themselves rather than separating sentence parts. They're about what's missing or who owns what.

Apostrophes for Contractions and Possession

• Contractions use apostrophes to mark missing letters—"don't" replaces "do not," with the apostrophe standing in for the missing "o"
• Singular possession adds apostrophe + s—"the dog's bone" means one dog owns the bone
• Plural possession for words ending in s adds only an apostrophe—"the dogs' park" means multiple dogs share the park

Ellipsis for Omitted Text

• Ellipses (three dots) indicate omission—use them when cutting words from a quotation
• Trailing thought can be shown with ellipsis in creative writing—"I thought I saw..."
• Maintain original meaning—cutting words shouldn't change what the author actually said

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Marks That Add Emphasis or Extra Information

These punctuation marks let you insert additional content into sentences without disrupting the main grammatical structure. They're about controlling emphasis and flow.

Parentheses for Additional Information

• Parentheses enclose supplementary details—information that clarifies but isn't essential
• The sentence must work without them—if removing the parenthetical breaks the grammar, restructure
• Lower emphasis than dashes—parentheses downplay information while dashes highlight it

Dashes for Emphasis or Interruption

• Em dashes create strong emphasis—they draw attention to inserted information or abrupt shifts
• Dashes can replace commas or parentheses when you want the interruption to stand out
• Use sparingly—too many dashes make writing feel breathless and fragmented

Quotation Marks for Direct Speech and Titles

• Direct speech requires quotation marks—distinguish between what someone said and your paraphrase
• Short work titles (articles, poems, short stories, songs) go in quotation marks; long works get italics
• American punctuation rule: commas and periods always go inside closing quotation marks

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Marks That Connect and Clarify

These smaller marks handle specific jobs: connecting compound words, formatting dates, and managing abbreviations.

Hyphens for Compound Words and Numbers

• Compound adjectives before nouns need hyphens—"well-known author" but "the author is well known"
• Numbers twenty-one through ninety-nine are hyphenated when written out
• Avoid over-hyphenation—only hyphenate when the compound modifies a noun that follows

Punctuation in Dates and Addresses

• Dates use commas to separate day from year—"July 4, 1776" with a comma after the year if the sentence continues
• Addresses separate elements with commas—street from city, city from state
• Consistency in formatting matters for formal documents and citations

Punctuation with Abbreviations and Acronyms

• Some abbreviations use periods (U.S., Dr., etc.) while others don't (NASA, FBI, CEO)
• Acronyms typically omit periods—especially well-known organizational names
• Match your source's style or follow a consistent style guide throughout your writing

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Capitalization Rules

• First words of sentences and proper nouns (specific names, places, organizations) are always capitalized
• Titles of works capitalize major words—nouns, verbs, adjectives—but not articles or short prepositions
• Common nouns stay lowercase unless they begin a sentence—"the president" vs. "President Lincoln"

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Quick Reference Table

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Self-Check Questions

1. What's the key difference between when you use a semicolon versus a colon to connect ideas?

2. Which two punctuation marks both indicate something is missing, and how do their uses differ?

3. Compare parentheses and dashes: if you wanted to emphasize an interruption, which would you choose and why?

4. A sentence joins two independent clauses with "and." When do you need a comma before "and," and when don't you?

5. You're quoting a source but need to cut some words. Which punctuation mark shows the omission, and what rule must you follow to use it ethically?