Punctuation

Punctuation gives a sentence rhythm and helps readers find its meaning. A comma can offer a breath; a period can let an idea land. Here’s how the small marks work.

5.1Types of Punctuation

Different marks do different jobs. Start with the effect you want the sentence to have.

• Periods, question marks, and exclamation marks close a sentence.
• Commas, colons, and semicolons shape the relationships inside it.
• Hyphens join words; en dashes connect ranges or parts of a phrase; em dashes mark breaks.
• Parentheses and brackets add context.
• Quotation marks identify quoted words; apostrophes show possession or missing letters.

The sections below explain each mark with examples.

5.2Formatting Punctuation

Use consistent punctuation and formatting to ensure readability and clarity.

5.2.1Emphasis and Punctuation

Style the words you want to emphasize. Surrounding punctuation stays unstyled unless it belongs to the fully emphasized phrase or sentence.

Example: We leave on Friday, not Saturday.

If a whole sentence is italicized or bold, include its punctuation in that formatting.

5.2.2Lists and Inline Elements

Keep bullet punctuation unstyled unless the whole item is emphasized. Apply emphasis to a label or key phrase with a clear purpose.

Example: Bring a raincoat, a notebook, and a pen.

For a website label or literal input, keep surrounding punctuation separate from the label or input itself.

5.2.3Parentheses and Quotation Marks

When emphasizing a word inside parentheses or quotation marks, style the word rather than the surrounding marks. If an entire parenthetical sentence is emphasized, style it consistently.

Example: The invitation says “casual,” so leave the suit at home.

5.2.4Accessibility Considerations

• Avoid using punctuation alone as a visual cue (e.g., bold exclamation points).

Screen readers may not detect or interpret the intended emphasis.

• When using formatting for emphasis, ensure it also conveys meaning without relying solely on visual presentation.

5.3Commas

Use commas to separate items, join independent clauses with a conjunction, or set off introductory and nonessential information.

Use the serial comma, sometimes called the Oxford comma, in a list of three or more items.

Example: Bring a blanket, a picnic basket, and a good book.

Example: After lunch, we walked along the river.

Commas between describing words

When two adjectives describe a noun independently, a comma usually separates them. These are called coordinate adjectives. Try adding and between them or reversing their order. If the meaning still works naturally, a comma is likely to fit.

Independent descriptions: We spent a warm, sunny afternoon by the lake.

The afternoon was warm and sunny. Sunny, warm afternoon also keeps the same basic meaning. When the words build on one another instead, leave out the comma.

Descriptions that build: She carried three small wooden boxes.

Three tells us how many small wooden boxes there were; small describes the wooden boxes. The adjectives do not work as a freely rearranged list.

A compound modifier does a different job: its words describe the noun together as one unit. Compare a warm, sunny afternoon with a sun-filled afternoon. See Compound Modifiers for when a hyphen helps show that grouping.

5.4Colons and Semicolons

Use a colon to introduce a list, explanation, or quotation after a complete introductory clause.

Example: Pack three things: a coat, a map, and a water bottle.

A semicolon can join closely related independent clauses without a conjunction.

Example: The café was closed; we made coffee at home.

5.5Apostrophes

• Use apostrophes for contractions and possessives.
• For singular proper nouns ending in s, add ’s (e.g., Steve Jobs’s favorite device).
• Avoid unnecessary apostrophes in plurals.

See also Possessives.

5.6Periods and End Punctuation

End a statement with a period and a direct question with a question mark. An exclamation mark can convey surprise, excitement, or urgency when that tone fits.

Statement: The picnic starts at noon.

Question: Should we bring a blanket?

Exclamation: You made it!

One exclamation mark is usually enough. Let the wording carry some of the feeling.

5.7Quotation Marks

Quotation marks distinguish someone’s exact words from your own. Use a consistent convention for outer and inner quotations. American styles commonly start with double marks; many British styles start with single marks.

Double outer marks: “Alex said, ‘Bring a jacket,’ so I did.”

In American styles, periods and commas usually sit inside the closing mark. In many British styles, their position follows whether they belong to the quoted words. Follow the convention for your piece, and preserve the source’s meaning.

American punctuation: She called it “a quiet afternoon.”

Logical punctuation: She called it ‘a quiet afternoon’.

Question marks follow the meaning: is the quoted material a question, or is the surrounding sentence asking one?

Quoted question: “Are we leaving?” Maya asked.

Surrounding question: Did she really say “tomorrow”?

5.8Dashes, Hyphens, and Slashes

5.8.1Dashes

Dashes do different jobs. The en dash (–) connects a range or parts of a larger phrase. The em dash (—) creates a break in a sentence. A hyphen (-) is a separate mark, usually used to join words.

At a glance: a five-minute walk; pages 12–18; I packed everything—except my keys.

See En Dash for ranges, open compounds, and phrases that use both hyphens and en dashes. See Em Dash for asides, emphasis, and interrupted speech.

5.8.1.1En Dash

An en dash (–) is longer than a hyphen and shorter than an em dash. Use it for compact ranges and, in some compound modifiers, to connect a whole phrase to another word.

Ranges and connections

An en dash can stand for to or through in a range of pages, dates, times, or other numbers. It can also connect the endpoints of a route. Leave no spaces on either side.

Ranges: pages 12–18; June 3–7; 9–11 a.m.

A connection: the Paris–London train

When you introduce a range with from or between, finish the pair in words: from … to or between … and.

In words: Read from page 12 to page 18, or choose a time between 9 and 11 a.m.

When one part is a phrase

A compound modifier is a group of words that describes a noun. Usually, a hyphen joins its words: a five-minute walk. But if one part is an open compound, a phrase written as separate words, an en dash can show that the whole phrase belongs with the word beside it. This guide follows that convention.

A place name: a New York–based writer

The writer is based in New York. The en dash connects based to the whole place name, while the space inside New York stays in place.

A brand name: New Balance–inspired sneakers

The design is inspired by New Balance as a whole. Keep the name’s own spacing and capitalization. A name used directly before a noun needs no extra mark: New Balance sneakers.

A familiar phrase: an ice cream–filled pastry

The filling is ice cream. If the phrase takes a moment to untangle, write a pastry filled with ice cream instead. The dash should help the reader, not give them a puzzle.

When hyphens and en dashes appear together

An en dash can connect two groups that already contain hyphens. Keep each group’s internal hyphens; use the en dash at the boundary between the groups.

One compound modifier: The shop offers a trade-in–trade-up program.

The hyphens hold trade-in and trade-up together internally. The en dash connects those two complete groups to make one modifier describing program. For a simpler version, write a program for trading in an old item and trading up to a new one.

A hyphen and an en dash can also appear in separate modifiers in the same sentence. Each keeps its own job.

Separate modifiers: She’s an award-winning, New York–based writer.

The hyphen joins award and winning. The en dash connects the whole place name New York to based. Here, award-winning and New York–based describe the writer independently; the two modifiers are separated by a comma.

One existing hyphen does not automatically call for an en dash. A prefix attached to a hyphenated compound generally takes another hyphen.

Hyphens throughout: a non-English-speaking visitor

These conventions vary among style guides. Whatever approach you choose, keep it consistent and rephrase when punctuation cannot make the meaning clear.

Typing an en dash

On a Mac with a U.S. keyboard layout, press Option + hyphen. On Windows, hold Alt and type 0150 on the numeric keypad. You can also use your app’s symbol picker or copy this character: –.

See Compounds and Prefixes and Compound Modifiers for the word forms behind these punctuation choices.

5.8.1.2Em Dash

An em dash (—) creates a strong break in a sentence. It can set off an aside, emphasize an ending, or show that a speaker has been cut off. Think of it as a change in the sentence’s rhythm.

An aside or an emphatic ending

Use a pair of em dashes to set off an aside within a sentence. The sentence around the aside should still make sense when you remove it. Use one dash when the added thought comes at the end.

An aside: The café—our usual Saturday stop—was closed.

An ending: I brought everything for the picnic—except the food.

Commas make an aside feel more connected to the sentence; parentheses make it feel quieter. An em dash gives it more emphasis. Choose the rhythm that suits what you mean.

Interrupted speech

In dialogue, an em dash can mark an abrupt interruption, even in the middle of a word. An ellipsis suggests that the speaker trails off instead. A dash that ends an interrupted line does not need an extra period.

An interruption: “I thought you said—” “I changed my mind.”

Trailing off: “I thought you said…”

Spacing and restraint

In this guide, em dashes touch the words on either side, with no spaces. Other styles use spaces around em dashes or use spaced en dashes for sentence breaks. Those are style choices; choose one approach for a piece and use it consistently.

Give each dash a reason to be there. If every sentence has an aside or a surprise ending, the effect wears thin. A comma, colon, or new sentence may make the thought clearer.

Use the actual dash character in finished prose rather than two hyphens. Keep em dashes out of number ranges and compound modifiers; those are jobs for en dashes and hyphens.

Typing an em dash

On a Mac with a U.S. keyboard layout, press Option + Shift + hyphen. On Windows, hold Alt and type 0151 on the numeric keypad. You can also use your app’s symbol picker or copy this character: —.

5.8.2Hyphens

Use hyphens to join words in a compound modifier or prevent an ambiguous reading. Check a dictionary for established forms.

Example: a well-known author; a five-minute walk; re-sign a letter.

Do not hyphenate an adverb ending in -ly and the adjective it modifies.

Correct: a highly rated restaurant

Incorrect: a highly-rated restaurant

See En Dash for compound modifiers that include an open phrase, such as New York–based, or two groups that already contain hyphens.

See Compounds and Prefixes for open, closed, and hyphenated forms. Compound Modifiers covers placement before and after a noun, -ly adverbs, and shared endings such as five- and ten-minute walks.

5.8.3Slashes

• Use slashes sparingly to indicate options or alternatives (e.g., and/or), line breaks in poetry, or to separate parts of a file path.
• Avoid using slashes in place of words in formal writing. Rephrase instead.

5.9Parentheses and Brackets

Use parentheses for supplementary information that does not interrupt the sentence’s main meaning.

Example: We’ll meet at the café (the one beside the library).

Use brackets for an editorial clarification inside quoted material.

Example: “She [Maya] brought the bread.”

Avoid nesting parentheses when a clearer sentence would do.

5.10Other Punctuation

5.10.1Ellipses

An ellipsis uses three dots to suggest a pause, a trailing thought, or words left out of a quotation. The single character (…) is convenient, while some publications use spaced periods (. . .).

A trailing thought: I thought I left it here…

For an omission in a quotation, use an ellipsis without changing the original meaning. Brackets can make your intervention clear; some citation styles omit them.

Omission: “We walked […] until we reached the lake.”

Choose one convention for the piece. In an essay or other cited work, check the citation style you’re using.

5.10.2Ampersands

In ordinary prose, and is usually easiest to read. An ampersand (&) works in names, familiar pairings such as Q&A, and short labels where space is tight.

Prose: Bring a notebook and a pen.

Short label: Questions & answers

Keep the ampersand when it belongs to a name. Elsewhere, choose it deliberately rather than swapping it for and at random.

5.10.3At Sign (@) and Number Sign (#)

The at sign (@) appears in email addresses and social handles. The number sign (#), also called a hash or pound sign, can introduce a number or a hashtag. Its name and meaning depend on the context.

Email: hello@example.com

Hashtag: #WritingEveryDay

A musical sharp sign (♯) looks similar to # but is a different character. Use the name and character your subject calls for.

5.10.4Miscellaneous

A symbol can make a number or idea easier to recognize. Use the conventional form for your subject, and spell it out when that would be clearer.

• An underscore (_) often appears in file names and code.
• A percent sign (%) expresses a proportion out of 100.
• A degree symbol (°) appears in temperatures and angles. Spacing depends on the unit convention.
• An asterisk (*) can point to a note or carry a special meaning in code.
• A tilde (~) can mean approximately, though about is often clearer in prose.
• A vertical bar (|) has specific uses in mathematics and computing.
• An interrobang (‽) combines a question mark and exclamation mark. It suits playful writing more than a formal reference.

Percentage: 85%

Angle: 90°

Temperature in SI style: 20 °C

Arithmetic: 3 + 2 = 5

For feet and inches, spell out the units in everyday prose. Prime and double-prime marks (′ and ″) are the typographic symbols; straight quotes are a plain-text substitute.