Types of Brackets: How They Are Used
Summary
All brackets enclose text in a document and set it off from surrounding content. There are four types of brackets in English typography, of which parentheses are the most commonly used, followed by square brackets:
- Parentheses or round brackets ( ) set off optional, additional information.
- Square brackets [ ] enclose words in a quote inserted by someone other than the original author. They are also used to show brackets within parentheses.
- Braces { } act as a stylistic alternative to parentheses to enclose a specific type of text throughout a document.
- Angle brackets < > may enclose editorial instructions, indicate placeholder text, or enclose URLs, and be used as an alternative to square brackets if needed.
Parentheses
Parentheses or round brackets (also known as curved brackets) are used to provide additional, optional information in a passage. Text enclosed in parentheses is essential neither to the meaning nor to the structure of the sentence.
- Some nocturnal animals (like bats) use echolocation to navigate in the dark.
- We accept all forms of payment (cards, bank transfers, cash).
- Parentheses (round brackets) enclose optional information.
- I want to do something fun (like that picnic last month).
- We kept driving in the dark. (There was nothing else to do.)
In British English, round brackets are usually just called brackets, while in American English, they are known as parentheses.
Square brackets
Square brackets are used in quoted text to enclose words added by someone other than the original author (e.g., an editorial comment or clarification).
- She said, “They [the employees] have the option to work remotely.”
The phrase “the employees” has been added to the quote for clarity (to explain what the pronoun “they” refers to).
- In his diary he writes, “The villany [sic] of the man is beyond comprehension.”
The word sic is added to the quote to indicate the spelling error was in the original text.
Square brackets are also used as brackets within brackets: to enclose parenthetical material that appears in text already inside parentheses.
- July was the hottest month on record (in a 150-year period [Table 1]).
- If you are looking for a hardy houseplant, the snake plant is almost unkillable. (For a complete list, see The Green Guide to Houseplants [1999]).
In British writing, nested parentheses are used within parentheses instead of square brackets within parentheses (round within round brackets instead of square within round brackets).
- American: Armadillos are Xenarthrans (placental mammals [like sloths and anteaters] native to the Americas).
British: Armadillos are Xenarthrans (placental mammals (like sloths and anteaters) native to the Americas).
Braces
Braces or curly brackets are generally used in mathematics and computing rather than formal English, but they are available as a stylistic alternative to parentheses to enclose a specific type of text throughout a document.
Some nouns are plural in form but singular in use and meaning {good news is always welcome} {economics is a challenging subject} {measles is potentially deadly}.
Braces instead of parentheses set off examples from surrounding text in the Chicago Manual of Style (17th ed.).
Although braces have no formal use in English, they can help improve clarity. For example, they can be used to present options and equal choices.
- You may pick any of the following sets of items: {a pencil, a sheet of paper, a magic eraser}, {a spoon, a lump of sugar, a magic bean}, or {a phone, a charger, a magic wand}.
Angle brackets
Angle brackets (indicated by the greater-than and less-than signs) are used frequently in programming and mathematics. In English, their only formal use is to enclose website names in some citation styles.
- “Sylvia Plath (American author),” Encyclopedia Britannica. <https://www.britannica.com/biography/Sylvia-Plath>, accessed Oct. 8, 2022.
Angle brackets are also used in software and applications to indicate placeholder text or a field where user input is required.
- Dear <NAME>,
- Press Enter, and type <your search query>.
A single closing angle bracket is used to provide simple technical instructions.
- Select Billing > Your Payments > Current Outstanding.
Angle brackets are not generally used in English prose, but they may be used by an author as a typographical preference. For example, in a text where square brackets are already heavily used in quoted content, angle brackets can be used instead of square brackets to add material to quoted text or provide editorial clarifications.
- In typical fashion, Woolf provides this information to us in brackets:
[Prue Ramsay died that summer in some illness connected with childbirth, which was indeed a tragedy, people said]
<my italics>.Ordinarily, a clarification to a quote (like the fact that a phrase has been italicized) would be enclosed in square brackets, but since brackets are already used in the original quoted text, the writer uses angle brackets instead.
Angle brackets may also be used by editors to enclose instructions for typesetters. (Such instructions are not seen in the final draft.)
Strictly speaking, angle brackets used in mathematics are represented by the symbols〈 〉, but most keyboards don’t have this symbol, and the greater-than and less-than signs < > are used instead in English.