Using Parentheses (Round and Square Brackets)

Our Story

Using Parentheses

(Round Brackets and Square Brackets)

Round brackets have three uses:

(1) To insert additional information into text.
  • The stegosaurus (the best-known herbivorous dinosaur) had a brain the size of a ping pong ball.
  • (The additional information is usually an expansion or clarification of whatever preceded or an afterthought.)
(2) To introduce an abbreviation.
  • Neil Armstrong was selected to join the National Aeronautics and Space Administration (NASA) in 1962.
(3) To show a plural option alongside a singular one.
  • Do not remove the pin(s) while the light is on.


Square brackets have two main uses:

(1) To show that text in a quotation did not feature in the original.

  • (1a) Square brackets can be used to explain something in a quotation.
    • Original quotation: "It is a contradiction in terms."
    • Amended: "It [military intelligence] is a contradiction in terms."
  • (1b) Square brackets can be used to modify a quotation.
    • Original quotation: "It is a contradiction in terms."
    • Amended: "[Military intelligence] is a contradiction in terms."
  • (1c) Square brackets can be used to replace unnecessary text with [...] (called an ellipsis).
    • Original quotation: "I don't want any yes-men around me. I want everybody to tell me the truth even if it costs them their jobs."
    • Reduced: "I don't want any yes-men around me [...] even if it costs them their jobs."
(2) To show that text in a quotation did feature in the original.
  • In your statement, you wrote: "I appraised [sic] him of the situation at about 4 o'clock."
  • (This should be "apprised" not "appraised." The term sic is short for sic erat scriptum ("thus it was written").)

More about Using Parentheses (Round Brackets)

(1) Using Round Brackets to Insert Additional Information into Text

parentheses (brackets) for additional information

Here are some more examples of using round brackets to insert additional information into text. (The additional information is usually an expansion or clarification of whatever preceded or an afterthought.)
  • The stegosaurus (a genus of herbivorous thyreophoran dinosaur) was predated by the allosaurus.
  • (The round brackets insert an expansion.)
  • The stegosaurus (the herbivore with tiles on its back and a spikey tail) weighed the same as a car.
  • (The round brackets insert a clarification.)
  • The plates on a stegosaurus's back were for display. (It is unlikely they had a thermoregulatory function like an elephant's ears.)
  • (The round brackets insert an afterthought.)
The additional information inside the brackets is called a parenthesis. A parenthesis can be removed without any loss of meaning.

(2) Using Round Brackets to Introduce an Abbreviation

If there's a chance your readers might not be familiar with an abbreviation, write it out in full the first time it's used and put the abbreviation in brackets afterwards. This is a standard practice in business and academic writing.
  • The Master of Business Administration (MBA) teaches approaches to business management.

(3) Using Round Brackets to Show a Plural Option

parentheses (brackets) to show plural option

For brevity, round brackets can be used to show a plural option.
  • Remove the sheet(s) so the air can flow freely
  • (This avoids "sheet or sheets.")
  • Please append the name of your guest(s) to the list.
  • (This avoids "guest or guests.")
When using brackets to show a plural option, it could start getting complicated if you provided an option with everything that ought to change.
  • Ensure the rod(s) is(are) aligned with the top section.
  • (This is untidy.)
  • The routine uses the output(s) of that(those) process(es).
  • (This is almost unreadable.)
The normal practice is to use (s) with just the key word and to treat everything else as singular.
  • The routine uses output of that process(es).
In a similar way, round brackets can be used to present two ideas at once. This is usually done for a bit of fun.
  • Bring your A game on Monday. We're going to crack Mission (Im)possible.
  • I'm calling it an (experi)mental project.

Why Should I Care about Round Brackets?

There are three noteworthy issues with brackets.

(Issue 1) Brackets are considered informal.

Brackets are a great way to add additional information because they're easy to spot. This means they won't disrupt reading flow. There's a problem though. Brackets are considered informal, and lots of businesses and universities do not permit their use in formal documents. Don't worry. There's a solution. Using brackets is just one of your options for inserting additional information. You can also use commas or dashes.
  • The stegosaurus, the best-known herbivorous dinosaur, had a brain the size of a ping pong ball.
  • (Commas are an alternative to round brackets.)
  • The stegosaurus – the iconic dinosaur that lived 150 million years ago – had a top speed of 5 mph.
  • (Dashes are another alternative to round brackets.)
Be aware that brackets trump commas and dashes when used like this:
  • A large stegosaurus could be 9 metres (29.5 feet) long and weigh 7 tons (15,432 pounds).
  • (Everyone permits brackets for this purpose.)
You Can Use Brackets, Commas, or Dashes


Even though they are useful for introducing information to make your writing clearer, round brackets can make your work look a little informal or disorganised. In formal correspondence, you should try to limit their use. Don't forget though, brackets are just one type of parenthetical punctuation.

Commas and dashes are options too. For example:
  • Fingers (real name Simon Smith) was caught by the police after he locked himself in the safe.
  • Fingers, real name Simon Smith, was caught by the police...
  • Fingers — real name Simon Betts — was caught by the police...
Read more about your choice of parenthetical punctuation.

(Issue 2) Uncertainty over whether a period goes inside or outside the close bracket.

The big question with brackets is where to put the end punctuation, which is usually a period (full stop). Does it go inside or outside the brackets?

When using brackets, the positioning of end punctuation follows logic. Sometimes it goes outside the close bracket, and sometimes it goes inside. For example:
  • She will ride a pony. (However, she will not ride a Dartmoor pony.)
  • (The period belongs to the full sentence in the brackets.)
  • She will ride a pony (but not a Dartmoor pony).
  • (The period belongs to the main sentence, not to the text in the brackets.)
  • She will ride a pony (she told me yesterday) but not a Dartmoor pony.
  • (The text inside the brackets (i.e., the parenthesis) is a standalone sentence within another sentence. When this happens, you should, for readability, start the parenthesis with a lowercase letter and omit the period.)
Things can get quirky with question marks and exclamation marks because you might need to double up on end punctuation. The principle is the same: end punctuation follows logic.
  • The group paid with a stolen credit card (my credit card!).
  • (The exclamation mark belongs with my credit card, and the full stop ends the whole sentence.)
  • The group paid with a stolen credit card (didn't you lose your card?).
  • (The question mark belongs with the bracketed question, while the full stop ends the sentence.)

(Issue 3) Uncertainty with capital letters when expanding an abbreviation.

When introducing an abbreviation, there's nothing to think about if the abbreviation represents the name of something (i.e., a proper noun). In other words, the expanded version is written with capital letters.
  • The motto for the Federal Bureaux of Investigation (FBI) is "fidelity, bravery, integrity".
If your abbreviation does not represent a proper noun, you must decide whether to use capital letters.
  • Food crops are the most controversial genetically modified organism (GMO).
  • (The full version of the abbreviation isn't immediately obvious.)
  • The term Genetically Modified Organism (GMO) was popularized by the media not scientists.
  • (The capital letters aren't justifiable under capitalization rules, but the definition of the abbreviation now stands out.)
So, each option has a pro and a con. If the institution you're writing for does not offer any guidelines on whether to go "caps" or "non-caps" in such cases, then pick a method and be consistent. (If you go for the "non-caps" option, you'll have far fewer pedants on your case.)

More about Using Square Brackets

(1) Using Square Brackets to Show That Text in a Quotation Was Not in the Original.

square brackets to explain quotations

Square Brackets to Explain Something in a Quotation

In these examples, the original text is intact, but an explanation is inserted using square brackets.
  • "Most people save all their lives and leave it [their money] to somebody else." (Actress Hedy Lamarr)
  • "It [electricity] is really just organized lightning." (Comedian George Carlin)
Square brackets tell your readers that the bracketed text did not feature in the original.

Using Square Brackets to Modify a Quotation

In the next examples, the original text has been modified. The words that needed explaining have been replaced with the explanations.
  • "Most people save all their lives and leave [their money] to somebody else."
  • "[Electricity] is really just organized lightning."
This technique can also be used to tweak the words in a quotation to ensure it aligns with your text.
  • Angela Merkel believes "it's [her] damn duty and obligation to do everything possible for Europe to find a united path."
  • (The original quotation was "It's my damn duty….")
  • Quoting author Flannery O'Connor, Jason often reminded his children that "[t]he truth [did] not change according to [their] ability to stomach it."
  • (The original quotation was "The truth does not change according to our ability to stomach it".)
Typically, aligning a quotation means changing a pronoun (e.g., "my"2 to "his") or changing a verb tense (e.g., "does" to "did"). Some people also like to show that a capital letter has been changed to a lowercase letter, as in the second example. (That's a bit much, IMHO.) If you find yourself tweaking other types of words, be careful not to change the intended meaning of the quotation. Also, if you find yourself over-tweaking, try to revert to the original quotation.
  • Alice Cooper famously said that "from the moment [he] leave[s] [his] house or hotel room, the public owns [him]."
  • (This is a mess.)
  • Alice Cooper famously said: "From the moment I leave my house or hotel room, the public owns me."
  • (This is much tidier.)
Using Square Brackets to Replace Unnecessary Text

square brackets with ellipsis (three dots)

Three dots (called ellipsis) are often used to show that text has been omitted from a quotation. An ellipsis punctuation mark is written "..." or "[...]".
  • Education is the most powerful weapon […] to change the world. (President Nelson Mandela)
  • (The ellipsis replaces the words "which you can use".)
  • Andy Warhol is the only genius […] with an IQ of 60. (US author Gore Vidal)
  • (The ellipsis replaces the words "I've ever known".)

(1) Using Square Brackets to Show That Text in a Quotation Was in the Original.

square brackets with sic

Using Square Brackets with [sic]

The term "[sic]" shows that the preceding text featured in the original quotation. Often, "[sic]" is used to indicate that a writing error was committed by the original author.
  • He claimed his statement was "appropriate and did not undermine the moral [sic] of our troops."
  • (It should be morale not moral.)
[sic] is the opening word of "sic erat scriptum" (Latin for "thus was it written"). It is not an acronym meaning "said in copy" or "spelling is correct." Therefore, [s.i.c.] is wrong. [sic] is not solely used for highlighting writing errors. It can be used to highlight unusual word usage (e.g., archaisms, dialectic language), surprising facts or facts known to be wrong.

Why Should I Care about Square Brackets?

(Reason 1) Square brackets allow you fit quotations snugly into your work.

Quotations are a great way to incorporate information from other sources into your writing, and they are particularly useful for supporting arguments. Quotations carry a sense honesty and believability. They're like an impartial vote for your assertion. You can use square brackets to trim quotations fit snugly into your writing. So, chop and change away, but remember not to change the intended meaning.

(Reason 2) Slam someone with [sic].

If you're ever the recipient of antagonistic correspondence that contains a writing error, you could use [sic] to slam the sender for their error.
  • Antagonist: I am not adverse to change, but I will not be voting for your proposal.
  • You: I'm pleased you're not adverse [sic] to change because my proposal has been approved.
  • (The antagonist should have used "averse." Using [sic] this way fairly aggressive. Use sparingly.)

A Video on Using Square Brackets

Here is a video summarizing the section on square brackets:

Slider

Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

See Also

Apostrophes Colons Commas Dashes Hyphens Semicolons Quotation Marks