Punctuation and Spelling

This page is part of our Editorial Style Guide.

On this page

• Oxford comma (aka serial comma)

• Spelling, hyphens, and compound words

  • Exceptions

• Contractions

• Ellipses

• Parenthetical elements and commas, em dashes, parens, brackets

• Bullets and lists

  • Example of our preferred method for parallel structure in bulleted lists

  • Example of mixed use of fragments and complete sentences (not parallel structure)

• Separator

Oxford comma (aka serial comma)

Always use the Oxford comma. (This differs from UCSF Style.)

Do say: This, that, and the other thing.

We brought oranges, apples, and persimmons.

Do not say: This, that and the other thing.

We brought oranges, apples and persimmons.

Rationale: simpler; easy to remember; ensures clarity; reads better, looks better; agrees with Chicago and Strunk and White.

Spelling, hyphens, and compound words

Visit Merriam-Webster for spelling and hyphenation. Generally, the first spelling is the recommended choice. More: see Chicago 7.89: Hyphenation Guide, including the Chicago Hyphenation Table (subscription required).

Exceptions

Compounds formed with prefixes are normally closed. However, we use the UCSF Style recommendation for words like co-author.

Do say:

• She was co-senior author of the study.

• Brian Shoichet co-led the research.

• A paper co-authored by Apollonio appeared in PLOS Biology.

• Co-authors of the paper included Ray Billings, PhD, and Patricia Wallford, PhD, who are postdoctoral fellows in the Shoichet Lab. [Do not use a hyphen in “postdoctoral.”]

Contractions

The careful use of contractions is acceptable, taking into account the tone, purpose, and audience for the content. Our tone for news and UFD (for example) isn’t strictly formal, and forbidding all contractions can make content sound stuffy. Bottom line: Don’t be scared of a few contractions.

Ellipses

See Chicago for details. The basics:

• Use ellipses to show gaps in quotes.

• Use three periods in a row, with no spaces between periods.

• Use a space before and after the ellipses unless adjacent to other punctuation such as a comma, period, or quotation mark.

Parenthetical elements and commas, em dashes, parens, brackets

The choice of punctuation for parentheticals is a judgment call based on the meaning and rhythm of the sentence.

• A comma indicates no change in emphasis, simply a slight interruption.

• The use of em dashes serves to explain or amplify—suggesting increased emphasis—and indicates a substantial interruption. Do not use spaces adjacent to em dashes. (UCSF Style is different, using spaces surrounding an en dash.)

• Parentheses denote an aside or explanation with decreased emphasis (skippable).

• Brackets are generally used for editorial comment or explanation [Editor’s note].

Bullets and lists

See Chicago 6.130: Vertical lists—capitalization, punctuation, and format.

Used carefully, bulleted or numbered lists can clarify and focus your content and make scanning and reading the page easier.

Use a numbered list if:

• The items need to be in a set order.

• Using numbers can aid discussion of, or reference to, items.

For consistency across our content, use sentence case for all bulleted and numbered lists; capitalize the first word of each item.

Example of our preferred method for parallel structure in bulleted lists

Using a parallel structure for your lists will ensure that items are either all complete sentences or all fragments. This is the preferred and easier method. Both fragments and complete sentences start with a capital letter (sentence case).

Example of mixed use of fragments and complete sentences (not parallel structure)

Mixed use doesn’t sound or look as good as parallel structure, but if you can’t use parallel structure for bullet items for some reason, follow this guide: If any of the list items is a complete sentence, use end punctuation on all items.

Here’s a mixed use example (that would be easy to change to parallel structure):

• Our department is ranked first in NIH funding.

• Top faculty members, dedicated staff.

• High residency match rates.

• The department has 87 graduate students enrolled and 434 alumni.

Separator

When separating groups of text, first consider if a comma and a space will work. If not, or if you prefer a different style of separation, we prefer but do not require the interpunct, which is also known as middot. An interpunct separates elegantly without being potentially confusing (as with pipe characters, which can resemble a lowercase L or the number 1) and without being visually overbearing (bullets). For instructions on how to type an interpunct, see Keyboard Input. For example, in an email signature:

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