Punctuation guide: Avoiding common usage errors

Contributors: Jake Trujillo

Single-quotation (‘) vs. double-quotation (“) marks

Direct quotes

Use double quotation marks to offset a direct quote.

• Tillman experienced “an extraordinary feeling of joy” as he danced with Rosie.

Use single quotation marks to offset a quote within a quote; they should never be used beyond a direct quote.

• “Tillman experienced ‘an extraordinary feeling of joy’ as he danced with Rosie.”

Brackets [ ] vs. parentheses ( )

Interjections

Like single quotation marks, brackets should only be used within direct quotations. Use brackets to offset explanations or comments that interrupt the original quote.

• Elizabeth explained, “Melissa [her neighbor] came over earlier with free Girl Scout cookies.”

Additional information

Whereas brackets are used to enclose interruptions within a quote, parentheses are used to enclose additional information in expressions that are not quoted.

• Melissa (Elizabeth’s neighbor) came over with free Girl Scout cookies.

Commas (,) vs. semicolons (;)

Compound sentences

Use a comma and a coordinating conjunction to join two independent clauses together.

• The student continued to do his homework after dinner, and he hoped to finish before bed.

Use a semicolon to join two related independent clauses together without a coordinating conjunction.

• The student continued to do his homework after dinner; he hoped to finish before bed.

Be careful to distinguish conjunctive adverbs (e.g. therefore, however, or otherwise) from coordinating conjunctions (e.g. and, but, or yet): semicolons introduce adverbs that precede the second independent clause, whereas commas introduce coordinating conjunctions.

• Conjunctive adverb example: The student continued to do his homework after dinner; however, he did not finish before bed.
• Coordinating conjunction example: The student continued to do his homework after dinner, but he did not finish before bed.

Units in a series

In a series of units/items, separate each unit/item with a comma.

• Skylar visited London, Manchester, and Dublin while in the UK.

However, if commas are used to separate multiple items within a single unit, use semicolons to separate each unit in a series.

• Skylar visited London, Manchester, and Dublin in the UK; Denmark, Norway, and Sweden in Northern Europe; and Germany, Austria, and Hungary in Eastern Europe.

Semicolons (;) vs. colons (:)

Amplification

Use a colon to introduce a unit or a series of units/items. Keep in mind that colons can attach an independent clause and a dependent clause (e.g. a series) as long as the independent clause comes before the colon. Semicolons cannot attach a dependent clause to an independent clause.

• One country borders Denmark: Germany.
• Nine countries border Germany: Denmark, Poland, the Czech Republic, Austria, Switzerland, France, Belgium, Luxembourg, and the Netherlands.

Whereas semicolons conjoin two related independent clauses, colons conjoin two clauses that are even more closely related.  Use a colon to attach an independent clause that amplifies or provides further explanation of the main clause.

• The dog was confused: he could not find the ball his owner had just thrown.
• The sign displayed a clear message: “Beware of dog.”

Hyphens (-) vs. dashes (—)

Compound terms and numerals

Use hyphens to conjoin multiple words into a unit. Modifiers (e.g. adjectives) that are conjoined with hyphens function together rather than individually.

• The part-time employee
• The editor-in-chief ‘s office

Use hyphens to conjoin numbers, including fractions, into a unit.  

• Seventy-two
• One-third

Range

Use hyphens to indicate a range between quantities (e.g. time or distance).

• 1996-2017
• 15-20 miles

Interruptions

Use em dashes to indicate an interruption or change in thought.

• The University of Nevada, Reno—Nevada’s first land-grant institution—was originally established in Elko in 1874, but relocated to Reno in 1886.
• The University of Nevada, Reno campus looks cohesive—even the new buildings have brick exteriors that coordinate with older buildings.