In this guide
- Use the Oxford comma and know which style guides skip it
- Place periods and commas inside quotation marks
- Tell hyphens, en dashes, and em dashes apart
Punctuation tells readers how to hear your sentence: where to pause, what belongs together, and who said what. Get it wrong and a sentence can change meaning entirely. “Let’s eat, Grandma” and “Let’s eat Grandma” are the classic proof.
American punctuation has a few habits that set it apart, especially with quotation marks, and the major style guides don’t always agree. This guide covers the rules for each mark, with real examples and notes on where the Chicago Manual of Style (books and many businesses), the AP Stylebook (journalism and PR), and APA style (academic and science writing) differ.
GrammarVista.com USA keeps it practical: if two styles are both correct, we’ll say so. For sentence-level issues like run-ons and fragments, see our grammar rules guide.
Commas
Commas cause more arguments than every other mark combined. Here are the uses that matter most.
The serial (Oxford) comma
The serial comma is the comma before and or or in a list of three or more items.
- With: We invited the neighbors, Dana, and Luis.
- Without: We invited the neighbors, Dana and Luis.
The second version can read as if Dana and Luis are the neighbors. Chicago and APA require the serial comma. AP style omits it in simple lists but adds it when leaving it out would cause confusion or when list items are complex. Read the full debate in our post on the Oxford comma.
Quick rule: Unless you write for a newsroom or follow AP, use the serial comma. It never causes ambiguity, and leaving it out sometimes does.
Introductory elements
Use a comma after an introductory clause or a long introductory phrase.
- When the meeting ended, everyone headed to lunch.
- After three rounds of edits, the proposal was ready.
- However, the budget hasn’t been approved.
With a short introductory phrase, the comma is optional: “In 2025 we opened two stores” and “In 2025, we opened two stores” are both fine. Add it whenever it prevents a misreading: “While we ate, the dog barked” needs the comma.
Nonessential clauses and that vs. which
If a clause adds extra information that you could delete without changing the core meaning, set it off with commas. If it identifies which thing you mean, don’t.
| Sentence | Meaning |
|---|---|
| My sister who lives in Denver is a nurse. | I have more than one sister; this one lives in Denver. |
| My sister, who lives in Denver, is a nurse. | I have one sister, and by the way, she lives in Denver. |
In American English, the common convention is that for essential clauses (no commas) and which for nonessential ones (with commas).
- The report that you sent is missing a page. (identifies the report)
- The report, which you sent Monday, is missing a page. (extra detail)
Chicago recommends this distinction for formal writing, and AP follows it too. British English uses essential which much more freely.
Comma splices
A comma alone can’t join two complete sentences.
| ❌ Avoid | ✅ Use |
|---|---|
| The store is closed, we’ll go tomorrow. | The store is closed, so we’ll go tomorrow. |
| I called twice, nobody answered. | I called twice; nobody answered. |
| It’s late, however, I’ll finish it. | It’s late; however, I’ll finish it. |
Other comma basics
- Direct address: “Thanks, Jordan.” / “Jordan, can you call me?”
- Dates: “On July 4, 1776, the declaration was signed.” Note the comma after the year in a full date.
- City and state: “She moved to Austin, Texas, last year.” The state is followed by a comma too.
- Coordinate adjectives: “a long, boring meeting” (you could say “long and boring”), but “a bright red car” (no comma).
Apostrophes
Apostrophes do two jobs: show possession and mark missing letters in contractions. They almost never make words plural.
Possessives
| Situation | Rule | Example |
|---|---|---|
| Singular noun | add ’s | the dog’s bowl, the boss’s office |
| Plural ending in s | add ’ only | the dogs’ bowls, the Smiths’ house |
| Plural not ending in s | add ’s | the children’s books, women’s rights |
| Joint ownership | ’s on the last name | Ana and Ben’s apartment |
| Separate ownership | ’s on each name | Ana’s and Ben’s phones |
Names ending in s
This is where style guides split. Chicago adds ‘s to singular names: James’s idea, Chris’s car. AP adds only an apostrophe to singular proper names ending in s: James’ idea, Chris’ car. Both are correct; choose one and stay consistent.
Plurals never get an apostrophe
Quick rule: If you just mean “more than one,” don’t use an apostrophe.
| ❌ Avoid | ✅ Use |
|---|---|
| Fresh bagel’s daily | Fresh bagels daily |
| The Johnson’s are coming. | The Johnsons are coming. |
| In the 1990’s | In the 1990s |
| She owns three DVD’s. | She owns three DVDs. |
For decades, write the 1990s, or the ’90s with the apostrophe facing the missing digits (it should look like a closing single quote, not an opening one). The most famous apostrophe trap of all is covered in its vs. it’s.
Semicolons
A semicolon has two main uses.
1. Joining closely related complete sentences without a conjunction:
- The flight was delayed; we missed our connection.
- She didn’t study; nevertheless, she passed.
2. Separating list items that already contain commas:
- The tour stops in Portland, Maine; Portland, Oregon; and Austin, Texas.
Don’t use a semicolon where a comma or colon belongs. “I need three things; coffee, quiet, and time” should use a colon.
Colons
A colon introduces something that explains, lists, or completes what came before. The part before a colon should be a complete sentence.
| ❌ Avoid | ✅ Use |
|---|---|
| The recipe needs: flour, eggs, and butter. | The recipe needs flour, eggs, and butter. |
| My favorite colors are: blue and green. | I have two favorite colors: blue and green. |
Colons also appear in times (9:30 a.m.), ratios (3:1), Bible verses, titles with subtitles, and American business letter salutations (“Dear Ms. Lee:”).
Capitalizing after a colon
- AP and APA: Capitalize the first word after a colon if it starts a complete sentence.
- Chicago: Lowercase the first word unless it’s a proper noun, begins a quotation, or the colon introduces two or more complete sentences.
Example (AP/APA): “The verdict was clear: The plan had failed.” Example (Chicago): “The verdict was clear: the plan had failed.”
Quotation Marks, American Style
American and British conventions differ most here. Follow these placement rules in American writing.
Quick rule: Periods and commas go inside. Colons and semicolons go outside. Question marks and exclamation points depend on meaning.
| Mark | Placement | Example |
|---|---|---|
| Period | Always inside | He said, “Let’s start.” |
| Comma | Always inside | “I agree,” she replied. |
| Colon | Always outside | There are two “rules”: arrive early and stay late. |
| Semicolon | Always outside | She called it “brilliant”; I called it lucky. |
| Question mark | Inside if the quote is a question | She asked, “Are you coming?” |
| Question mark | Outside if the whole sentence is the question | Did he really say “no comment”? |
Double outside, single inside
Americans use double quotation marks first and single quotation marks for a quote within a quote:
- “My boss told me, ‘Take Friday off,’ so I did,” Sam said.
British publishing often reverses this. See the American vs. British English guide for more side-by-side differences.
Other uses
Use quotation marks for titles of short works (articles, songs, episodes, chapters) and italics for long works (books, movies, albums) in Chicago and APA. AP uses quotation marks for most composition titles because it doesn’t use italics. Avoid “scare quotes” for emphasis: a sign reading “Fresh” Fish suggests the fish isn’t fresh at all.
Hyphens, En Dashes, and Em Dashes
These three marks look similar but do different jobs.
| Mark | Symbol | Main job | Example |
|---|---|---|---|
| Hyphen | - | Joins words | a well-known author |
| En dash | – | Ranges, complex compounds | pages 10–15 |
| Em dash | — | Breaks or emphasis | The answer—finally—was yes. |
Hyphens and compound modifiers
Hyphenate two or more words that work together as a single adjective before a noun. After the noun, the hyphen usually drops.
- She’s a well-known author. / The author is well known.
- We need a full-time designer. / She works full time.
- It was a last-minute change.
Quick rule: Never hyphenate after an -ly adverb. Write “a highly rated restaurant,” not “a highly-rated restaurant.”
En dashes
Chicago and APA use the en dash for number ranges (2020–2024, 9:00–5:00) and for compounds involving open terms (a New York–based firm). Don’t mix a range with from or between: write “from 2020 to 2024,” not “from 2020–2024.” AP style does not use en dashes; it uses a hyphen for ranges.
Em dashes
An em dash sets off an interruption, a sudden turn, or an emphatic aside. It’s punchier than commas and less formal than parentheses.
- The results—all three of them—were positive.
- She had one goal—win.
Chicago closes up em dashes with no spaces (word—word). AP puts a space on each side (word — word). Use two hyphens only if your software truly can’t produce an em dash.
Ellipses
An ellipsis (…) shows omitted words in a quotation or a trailing-off thought.
- Original: “We will review, approve, and publish the report next week.”
- Shortened: “We will … publish the report next week.”
When an omission follows a complete sentence, keep that sentence’s period, then add the ellipsis. Chicago traditionally uses spaced periods (. . .), while AP treats the ellipsis as a three-character word with a space on each side. Never use an ellipsis to change a speaker’s meaning. In texts and casual messages, a trailing “…” can read as hesitant or passive-aggressive; our text slang at work post explains why tone matters there.
Parentheses and Brackets
Parentheses hold extra information the sentence could live without.
- The conference (our largest yet) sold out in a week.
- Submit the form by Friday. (Late forms won’t be accepted.)
Quick rule: If the parenthetical is a full sentence on its own, the period goes inside. If it’s part of a larger sentence, the period goes outside.
Square brackets mark your own changes or clarifications inside a quotation:
- “She [the mayor] approved the plan.”
- “Their [sic] going to win,” the sign read.
Sic signals that an error appeared in the original. APA also uses brackets for parentheses inside parentheses.
Question Marks and Exclamation Points
Use a question mark only after a direct question.
- ✅ Can you send the file?
- ✅ I wonder whether she’ll call. (indirect question, period)
- ❌ I wonder whether she’ll call?
Polite requests in emails can take a period: “Could you please review this by Tuesday.” Both a period and a question mark are accepted there.
Use exclamation points sparingly, and never stack them in professional writing. One is plenty, and in formal writing, zero is usually better. Never combine a question mark and an exclamation point (?!) outside casual messages.
Quick Checklist
- Use the serial comma unless you’re following AP style.
- Put a comma after introductory clauses and long phrases.
- Use that without commas for essential clauses, which with commas for extras.
- Never join two complete sentences with only a comma.
- Use apostrophes for possession and contractions, never for plurals (1990s, DVDs).
- Choose James’s (Chicago) or James’ (AP) and stay consistent.
- Use a semicolon between related sentences or in complex lists.
- Put a complete sentence before a colon.
- Place periods and commas inside quotation marks; colons and semicolons outside.
- Hyphenate compound modifiers before a noun, but never after an -ly adverb.
- Use en dashes for ranges and em dashes for emphasis, following one spacing style.
- Use one space after a period.
Frequently Asked Questions
Does the period go inside or outside the quotation marks in American English?
Inside. American style places periods and commas inside closing quotation marks every time, as in: She said, "I'll be there." British style often places them outside unless they belong to the quoted material.
Is it Chris's or Chris' for a name ending in s?
It depends on the style guide. The Chicago Manual of Style recommends Chris's, while the AP Stylebook uses just an apostrophe for singular proper names ending in s, as in Chris' car. Pick one and stay consistent.
Should I put a space before and after an em dash?
Chicago and most book publishers use no spaces around an em dash. AP style puts a space on each side. Both are correct as long as you follow one approach throughout a document.
How many spaces go after a period?
One. Major American style guides, including Chicago, AP, and APA, call for a single space after a period in normal text. Two spaces is a holdover from the typewriter era.
Can you use a semicolon before "and"?
Usually not. A semicolon normally replaces "and" between two complete sentences. The exception is a complex list whose items already contain commas, where semicolons separate the items, including before the final "and."