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English punctuation: commas, semicolons and colons

Choose the right punctuation mark using paired sentence examples, with notes for common US English conventions.

40 entries

When to use semicolons

Join related sentences: The server is ready; the clients are not.
Both halves are independent clauses; a semicolon can link them without a conjunction. [2][1]
With “however”: The device was fast; however, it ran hot.
A transitional adverb joining clauses normally takes a semicolon before and a comma after it. [2][1]
With “therefore”: The inputs changed; therefore, we reran the test.
Use semicolon plus a transitional word between two complete clauses. [2][1]
Without a conjunction: We tested the prototype; the logs confirmed the result.
Use a semicolon when closely related statements each stand on their own. [2][1]
With “and” instead: We tested the prototype, and the logs confirmed it.
When coordinating conjunction and joins two complete clauses, use a comma. [2][1]
Avoid a comma splice: Not: The file grew, the drive filled.
Two complete clauses should not be joined with only a comma in conventional formal prose. [2][1]
Avoid a fragment after it: Not: We paused; because of the weather.
The second part is not an independent clause. [2][1]
Separate complex list items: Guests: Ana, Lisbon; Bo, London; and Kim, Seoul.
Semicolons can distinguish list items containing internal commas. [2][1]
Avoid using one in place of a colon: We packed three items: rope, food, and water.
A colon introduces a promised list; a semicolon does not. [2][1]
Before a conjunctive transition: It looked simple; nevertheless, it took hours.
Put a semicolon before a transitional adverb between independent clauses. [2][1]

When to use colons

Introduce a list after a sentence: Pack three things: gloves, a hat, and boots.
Text before a list-introducing colon should form a complete clause. [1]
Explain an assertion: One issue remained: the sensor had no power.
The second clause explains or specifies the first. [1]
Introduce a formal quotation: The report concluded: “More testing is needed.”
A colon may introduce a quotation after a complete introductory clause. [1]
Use in labels: Subject: Request for access
Colon separates a label and its corresponding value. [1]
Use in time: 09:30
Colon conventionally separates hours and minutes. [1]
Use in ratios: The scale is 1:5.
Colons can express ratios; match scientific or house-style conventions. [1]
Avoid between verb and object: Not: Bring: soap and towels.
Do not interrupt a verb directly followed by its objects. [1]
Avoid after a preposition: Not: The set includes: red and blue.
Includes already grammatically introduces the objects. [1]
Capitalization after a colon: The result was clear: the gate was closed.
Capitalization after colons varies by style and sentence type. [1]
Colon vs semicolon: Choose: The gate failed: its fuse was blown.
A colon introduces an explanation; a semicolon simply links related clauses. [1]

Useful comma decisions

Before a coordinating conjunction: The sample passed, but the control failed.
Place a comma before but connecting two independent clauses. [3][2]
After an introductory clause: When the bell rang, the class began.
A dependent opener usually takes a following comma. [3][2]
After an introductory transition: However, the result changed.
Introductory transitions normally have a comma. [3][2]
Set off nonessential detail: Maya, the lead designer, approved it.
The inserted identifying detail can be omitted without changing who Maya is. [3][2]
Essential detail without commas: The scientist who called is here.
The who-clause identifies which scientist; do not set it off as an aside. [3][2]
Three-item list: We checked color, size, and weight.
Oxford/serial comma is common in US formal prose; follow your chosen style. [3][2]
Pair coordinate adjectives: A small, noisy fan ran.
Use a comma for adjectives that can be joined naturally with and. [3][2]
No comma in compound adjective: The high-speed link worked.
High-speed is one hyphenated compound modifier before the noun. [3][2]
Direct address: Thanks, Alex, for the update.
Set off a person's name when directly addressing them. [3][2]
Comma vs semicolon: The chart changed, and the report was updated.
Use a comma with and; without the conjunction, consider a semicolon or period. [3][2]

Dashes, parentheses and quotations

Parenthetical aside: The run (our third attempt) succeeded.
Parentheses set off background information that is less central. [1][4]
Em dash for emphasis: One error remained—the missing key.
An em dash makes a stronger break than parentheses or commas. [1][4]
Paired em dashes: The team—after one more check—approved the plan.
Pair dashes around a mid-sentence interruption. [1][4]
Hyphenate compound modifier: It was a well-tested design.
Hyphens join a compound before the noun when clarity requires it. [1][4]
Quotation marks for exact wording: She wrote, “The build passed.”
Quotation marks identify the exact words being reproduced. [1][4]
Periods inside US quotation marks: She called it “stable.”
In conventional US punctuation, periods ordinarily go inside the closing quotation mark. [1][4]
Colons outside closing quotes: The label read “Run”: it was the wrong button.
Colons sit outside quotation marks in US convention. [1][4]
Semicolons outside closing quotes: The menu said “Stop”; we clicked it.
Semicolons also stay outside closing US quotation marks. [1][4]
Question mark in a quoted question: She asked, “Is it ready?”
The question mark belongs inside because the quoted sentence is itself a question. [1][4]
Question about a quoted phrase: Did he call it “ready”?
The question belongs to the outer sentence, so the mark falls outside. [1][4]

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Updated 2026-10-20US English · general prose

Sources

cheatsheetatlas.com/sheets/punctuation/ · Updated 2026-10-20 · US English · general prose

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