What Are Square Brackets ( [ ) And How Do You Use Them?

Of the different types of brackets, most people would likely say that parentheses are the ones they know the best. Going further, some people may not even know that there are other types of brackets. While square brackets may not be used very often, they are often crucial to writers who are wrangling an especially difficult quote. You never know when this poor writer might be you, so it is a good idea to be prepared and learn the best ways to use square brackets in your writing.

What are square brackets?

Square brackets, often just called brackets in American English, are a set of punctuation marks that are most often used to alter or add information to quoted material. Square brackets come in pairs as [ and ]. Square brackets resemble and are used similarly to parentheses, but these two punctuation marks are NOT used interchangeably.

When do you use square brackets?

In general, square brackets are used much less often than parentheses in writing. Most of the time, they are used to alter or provide additional context to quotes. Often, writers will adjust their work or rephrase the text around a quote so as to avoid having to use square brackets at all. Sometimes, though, using square brackets might be unavoidable so it is good to learn when you may need to use them.

Quotations

Typically, the most common reason you would need to use square brackets has to do with quotations.

All style guides, grammar resources, and ethical guidelines will tell you that it is not acceptable to change the wording of a quote so as to change its meaning or attribute words to a person that they never said.

However, sometimes it is necessary to adjust a quote or provide additional context to it so as to help a reader understand what was being said. Square brackets allow you to do this while making it clear that whatever is in the square brackets was not part of the original text or statement.

When it comes to quotes, there are several different reasons to use square brackets.

Clarification

Sometimes, a quote doesn’t make sense outside of the context it was originally used in or it references something else said earlier. In this case, a writer can use square brackets to add clarifying information for a reader. For example,

• Original statement: “I love my cat. Her name is Nina, and she is a great hunter. Nina loves eating mice and killing birds.”
• Quote with square brackets: He said, “Nina [his cat] loves eating mice and killing birds.”

Adding more information

Sometimes, a quote needs additional information that was never said originally in order to make sense to a reader. Again, we can use square brackets to add this information:

• Original statement: “This is a momentous day. These two nations have joined in friendship, and I am honored to have been a part of it.”
• Quote with square brackets: The ambassador said it was “a momentous day.” Going further, she said, “These two nations [Rohan and Gondor] have joined in friendship.”

Adjusting a quote for grammatical reasons

Sometimes, a quote doesn’t match grammatically with a writer’s text. For example, the original speaker may have been talking in the first person, but a writer is quoting them in the third person. Square brackets can be used to signal that a writer is adjusting a quote for grammatical reasons.

• Original statement: “I like mayonnaise. I even put it on hot dogs.”
• Quote with square brackets: She said that “[she] like[s] mayonnaise” and that “[she] even put[s] it on hot dogs.”

Noting a grammar error that was in an original quote

Because most writers will not change quotes at all, some quotes may contain grammar errors, misspellings, or other mistakes. Square brackets can be used to indicate to a reader that the error was present in the original source. In this case, the term sic is often used within the square brackets to state that the error was present in the original source. 

• Original statement: “The largest dessert on Earth is actually located in Antarctica.” 
• Quote with square brackets: I was surprised to learn the largest desert was actually in a cold place. My geography textbook says, “The largest dessert [sic] on Earth is actually located in Antarctica.” 

Parentheses within parentheses

Some style guides or grammar resources may allow using square brackets to avoid using a set of parentheses within another set of parentheses. For example,

• Joe did everything himself. (He never asks me [or anyone else] for help.) 

However, the rules regarding this particular case are not universal. It is best to consult the style guide or grammar resource you use if you ever encounter this situation. 

How to use square brackets

For the most part, square brackets follow all of the same rules of parentheses. However, square brackets are generally easier to use because they typically do not contain full sentences. 

Square brackets always come in pairs

Like parentheses, it is considered a grammatical error to use only a single square bracket. The additional information should be entirely contained within two square brackets:

❌ Incorrect: Leslie Mitchells of Canada] won the gold medal.
✅ Correct: Leslie Mitchells [of Canada] won the gold medal.

Capitalization

The first letter in square brackets typically isn’t capitalized because square brackets usually contain sentence fragments, single words, or single letters/symbols. However, proper nouns are typically capitalized even when used alone in square brackets. 

✅ Correct: Zach said, “I can teach [yoga] to anyone who is willing to learn.”
✅ Also correct: Whoville authorities are looking for “a grouchy green monster who hates [Christmas].”

Punctuate perfectly with Grammar Coach™

Confused about punctuation and its proper use? The Thesaurus.com Grammar Coach™ platform makes writing papers, essays, emails, and a whole lot more a whole lot easier. This writing tool uses machine-learning technology uniquely designed to catch grammar as well as spelling errors. Its Synonym Swap will find the best nouns, adjectives, and more to help say what you really mean, guiding you toward clearer, stronger, writing.