Parentheses and Brackets

Parentheses (the round ones) and brackets [the square ones] might look like headphones for words, but actually, both are used to insert text into other text. That said, although they occasionally work together, their functions are mostly quite different. Allow us to explain:

Parentheses

You'll probably be using parentheses primarily to set off acronyms or, depending on your citation style, in-text citations.

1. To introduce an acronym, first spell it out in your text, placing the acronym in parentheses; subsequent uses of the acronym take no parentheses:
    

   An increasingly important technology in expeditionary delicatessen operations is the sandwich-defined network (SDN). Though initially described as "baloney" by its wryer critics, over the past decade, refinements to SDN have rolled out . . . 

2. Certain citation styles, such as APA, Chicago Author-Date, and INFORMS, place citations in parentheses; see the NPS Citation Guide for more information:
    

   Though initially described as "baloney" by its wryer critics, over the past decade, refinements to SDN have rolled out, allowing it to catch up with the needs of ham operators, who now relish the technology (Coburg 1998, p. 11). 

3. Parentheses can also set off additional information inside a sentence. (They can even contain whole sentences.) However, doing so will signal to readers that this information is significantly less important than the surrounding text; be sure not to place critical material in parentheses! 

This research investigates whether three taxa of dough-enfolded comestibles (hot dogs, gyros, and hand pies) qualify as sandwiches. ←Case selection is likely too important for parentheses!

In situations like this one, dashes—or simply eliminating the appositive—are stronger (i.e., more emphatic) alternatives:

• This research investigates whether three taxa of dough-enfolded comestibles—hot dogs, gyros, and hand pies—qualify as sandwiches.
• This research investigates whether hot dogs, gyros, and hand pies qualify as sandwiches.

Brackets

Square brackets also have a role to play in in-text citation styles, as well as in quotations and translated sources:

1. When the author of a source is an organization widely known by an acronym, the first in-text citation can define that acronym:

   (Joint Chiefs of Staff [JCS] 2017)

   As in the text, subsequent citations can use the acronym only:
    

   (JCS 2017)

2. Use square brackets when modifying a quotation:

   As Drezner observes, “the challenges [flesh-eating zombies] pose to states are very, very grave.” (source)

3. Square brackets enclose translated titles in the list of references; see the Essential Rules page of your citation style for more information. 
    

Still have questions about parentheses and brackets? Make a coaching appointment or see the links below. 

Parentheses and Brackets Links

• GWC video (1:42): "Parentheses"
• Website: The Punctuation Guide