Punctuation Guide
Clear rules and real examples for the five most misused punctuation marks. Select a mark to see its rules.
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:
—
-
The Comma
The most frequently misused mark in English writing.
1. Serial Comma (Oxford Comma)
Use a comma before "and" or "or" in a list of three or more items. The Oxford comma prevents ambiguity.
With Oxford comma
I had eggs, toast, and orange juice.
Without: "I dedicate this book to my parents, Ayn Rand and God." (Are your parents Ayn Rand and God?)
2. Joining Independent Clauses
Use a comma + coordinating conjunction (for, and, nor, but, or, yet, so — FANBOYS) to join two complete sentences.
She studied all night, but she still failed the exam.
Wrong: She studied all night but she still failed the exam. (comma missing before "but" joining two clauses)
3. After Introductory Elements
Use a comma after introductory phrases, clauses, and transitional words.
After the long meeting, everyone needed coffee. / However, no one had brought any.
4. Nonrestrictive Clauses
Use commas around clauses that add information but don't identify the subject (nonrestrictive). No commas for restrictive clauses that define which one.
Nonrestrictive (extra info)
My sister, who lives in Paris, called me. (I only have one sister)
Restrictive (identifies which)
The student who studied hardest passed the exam.
The Semicolon
Stronger than a comma, weaker than a period.
1. Joining Related Independent Clauses
Connect two closely related complete sentences without a conjunction. The relationship should be clear without needing "and" or "but."
She studied for weeks; she still failed the exam.
Wrong: She studied for weeks; because she was unprepared. ("because she was unprepared" is not an independent clause)
2. With Conjunctive Adverbs
Use semicolon before words like however, therefore, moreover, furthermore, consequently, nevertheless.
The project was behind schedule; however, the team stayed late and finished it.
3. Complex Lists
Use semicolons to separate list items that already contain commas (the "super-comma").
We visited Rome, Italy; Paris, France; and Barcelona, Spain.
The Colon
Announces what follows. "As follows," "here it is," "namely."
1. Introducing a List
Use after a complete sentence that introduces a list. Never use a colon directly after a verb or preposition.
The kit includes three items: a brush, a comb, and scissors.
Wrong: The kit includes: a brush, a comb, and scissors. (colon after a verb — remove the colon)
2. Introducing Explanation or Elaboration
Use to introduce an explanation, elaboration, or restatement of what was just said.
There was only one problem: nobody had the key.
3. Introducing Quotations
Use before a long or formal quotation introduced by a complete sentence.
Churchill said it plainly: "We shall fight on the beaches."
The Em Dash —
Longer than a hyphen. Created with — or option+shift+hyphen on Mac.
1. Setting Off Parenthetical Information (Emphatic)
Em dashes set off an interruption or aside with more emphasis than parentheses, and more drama than commas.
The decision — and it was a costly one — changed everything.
2. Introducing a Trailing Explanation
Use an em dash before a summary, elaboration, or dramatic conclusion at the end of a sentence.
He had everything money could buy — and still he wasn't happy.
3. Interruption in Dialogue
In fiction and transcription, use an em dash to show an abrupt interruption in speech.
"I just wanted to say that I—" "Don't bother," she interrupted.
The Hyphen -
Shorter than a dash. Joins words together.
1. Compound Modifiers Before a Noun
Hyphenate compound adjectives that come before the noun they modify. Usually no hyphen after the noun.
Before noun (hyphen)
A well-known author wrote the book.
After noun (no hyphen)
The author is well known.
2. Compound Numbers and Fractions
Hyphenate compound numbers (twenty-one through ninety-nine) and fractions used as adjectives.
thirty-three years old / a two-thirds majority
3. Prefixes with Proper Nouns
Hyphenate when a prefix precedes a capitalized word, a number, or would create a confusing double vowel.
post-Brexit / mid-1990s / co-owner / anti-inflammatory