It’s not often that a punctuation mark comes as a mirrored pair. Ellipses are a succession of three periods and the interrobang is a merging of the question mark into the exclamation point. And while the colon and semi-colon can be considered a punctuation pair, they arrive to the party together and never leave each other’s side.
You can refer to the first of the two parentheses as simply a parenthesis, but you can’t have one without the other. One bracket is grammatically incorrect until its second reflected pair is placed.
While parentheses and brackets do have a similar shape and similar role in how they are used in a sentence, brackets and parentheses cannot be used interchangeably. Both pairs each have a distinct role that they play in a sentence to add more clarity and coherency.
So what’s the difference between parentheses and brackets? Read on, my friend.
Parentheses (Round Brackets)
Parentheses (or round brackets, especially in British English) separate information that isn’t exactly essential to the meaning of the rest of the sentence. In other words, the sentence would read smoothly and logically without the words sandwiched in between the parentheses.
Lake Superior (found between the Upper Peninsula of Michigan and Ontario, Canada) is the deepest of the Great Lakes.
Many articles have been published on this topic (see page 248).
Heather wanted to go home as soon as the party began (and so did I).
Special Uses of Parentheses
Parentheses can be used for lettered or numbered lists.
Example: The interview process for this position will follow these steps: (1) a review of your cover letter and resume, (2) a phone interview with our HR manager, and (3) an on-site interview with the hiring manager.
Parentheses can enclose time zones that follow after a stated time.
Example: The live broadcast will premiere at 8PM (CST).
Parentheses are often used to enclose area codes for a telephone number.
Example: Questions? Call us at (312) 555-5555.
Parentheses can also clarify short translation in unquoted passages or sentences.
Example: During Rose and Xavier’s date, he spoke some French, such as merci (thank you) and bonne nuit (goodnight).
Parentheses can also spell outacronyms or abbreviate phrasesto their known acronym.
Example: The tech company promoted Clarice to CPO (Chief People Officer).
Example: John’s parents are still learning texting lingo, such as IDK (I don’t know) and IMO (in my opinion).
Parentheses, in some writing, can be used to denote a person’s year of birth and/or year or death. Any uncertainty about the year should be followed by a question mark while an en dash is to be used between the years noted:
Example: Sister Maria Celeste (1600–1634), born Virginia Galilei, was the daughter of the famous Italian scientist Galileo Galilei.
Brackets [Square Brackets]
Brackets (or square brackets, especially in British English) add words to a sentence that are not the original writer’s or speaker’s words. This is often done to add further clarification to what is being stated.
Example: She [the assistant principal] punished the students with a week of detention.
Specialized Uses of Brackets
Brackets are often used to quietly change the first letter of quoted material from lowercase to uppercase, or the reverse:
Example: “[T]he jury is out until further notice.”
Example: According to her contract, her “[l]ength of employment may be extended with the extension of assigned project by the hiring company.”
The most common short-use form of brackets is when applying [sic]. This Latin term, meaning “so” or “thus,” is added to quoted material to indicate an error or confirm an unusual usage in the quoted passage. Without [sic], the reader could incorrectly assume that the writer providing the quoted passage made the error. Brackets are used around the italicized word, but the brackets themselves are not in italics.
Example: According to the eyewitness report, “Lloyd and George was [sic] at the automotive plant by 9AM.”
Brackets can also clarify short translation in quoted passages or sentences:
Example: Here’s what the article says: “The police arrested him at his Parisian home on Fête Nationale [Bastille Day].”
Brackets can also verify added emphasis into a quoted passage by the writer.
Example: Professor Walters said he would consider “adding extra credit to the final exam, but only if every student attended every lecture for the remainder of the semester [emphasis added].”
Brackets are used to blank out objectionable content so that the quoted passage is appropriate to be read by all readers.
Example: The teacher told the class to “sit the [explicative] down.”
Grammar Rules for Parentheses and Brackets
If the parentheses or brackets occur at the end of the sentence, then the sentence’s proper punctuation is placed outside of the closing parenthesis or bracket.
Example: After rehearsing for weeks, the cast wasn’t sure if they’d be ready to perform by opening night (or, in fact, ever).
If the parentheses or brackets occur in the middle of the sentence, then any punctuation within the sentence must be placed outside of the parentheses or brackets. Simply, all sentence punctuation must act as if the parentheses or brackets did not exist in the sentence.
Example: We went to the park (the one down the street), but we found it closed for renovations.
If the words within the parentheses or brackets form a complete sentence that can stand on its own, then it needs to be structured like a complete sentence with the correct capitalization and end punctuation. The sentence within the parentheses or brackets would stand apart as its own sentence.
Example: The corner store gave away last year’s textbook editions for free. (I wish I had known that before I bought mine online two days ago.)
These rules don’t apply to a sentence between parentheses or brackets that occurs in the middle of a larger sentence. When this happens, you do not capitalize the first word, unless it’s a proper noun, and you do not use punctuation except if the phrase is a question or exclamation.
Example: Quinn and I went over to Darla’s house (she lives in the suburbs now) and found that each of us brought over the same casserole (how did we manage to do that?).