Curly Brackets in English: Writing, Math & Programming with Examples

In my first ESL classes, students ask about curly brackets with obvious confusion: “Are these important? When do I actually use them?” The honest answer is nuanced. For everyday writing, you’ll rarely use them. But if you’re writing mathematical formulas, reading programming code, or crafting formal academic work, curly brackets serve specific, crucial functions. You’ll walks you through all three contexts — writing, mathematics, and programming — so you know exactly when and why to use them.

Curly brackets, also called braces or curly braces, are one of four bracket types in English. Understanding the full set — parentheses ( ), square brackets [ ], angle brackets < >, and curly brackets { } — will help you read and write across multiple disciplines with confidence.

Understanding All Bracket Types

Before diving into curly brackets specifically, it’s useful to compare all four bracket types used in English and technical writing. Each has a distinct purpose and appearance.

Bracket Type	Symbols	Main Uses	Example
Parentheses	( )	Add extra information or asides; group elements in mathematics	She went to Paris (her favourite city) last summer.
Square brackets	[ ]	Insert clarifications into quotes; array indexing in programming	“He said [the event] was postponed.” (original: “the meeting”)
Angle brackets	< >	Email addresses, HTML/XML tags, comparison operators	Email: contact@example.com or This is HTML.
Curly brackets	{ }	Sets in mathematics; code blocks in programming; formal grouping	Set A = {1, 2, 3} or for (let i = 0; i < 10; i++) { code }

Curly Brackets in Formal Writing

In everyday formal English writing, curly brackets are uncommon. However, they have specific legitimate uses in academic and technical writing contexts.

When to Use Curly Brackets in Writing

1. Showing alternatives or options — Curly brackets can indicate that you’re presenting choices or alternatives, though braces or parentheses are more common today.

Example: The conference will be held {Monday or Tuesday}, depending on venue availability.

2. Grouping related items in formal lists — When you need to group items that belong together within a larger context.

Example: The subjects covered include {Mathematics, Physics, Chemistry} in the sciences, and {History, Geography, Economics} in the social sciences.

3. Indicating a correction or editor’s note — In academic or journalistic writing, curly brackets (or sometimes square brackets) can indicate an editor’s insertion or clarification. However, [square brackets] are more standard for this purpose.

Example: The author wrote, “We must address the {environment} crisis immediately.” (The original said “climate” but was changed for clarity.)

Important: Curly Brackets Are Rarely Needed in Modern Writing

Most modern English writing avoids curly brackets. Instead, use:

• Parentheses ( ) for asides and extra information
• Square brackets [ ] for editorial notes and corrections
• Commas or em dashes for grouping related ideas

Instead of: “I need {paper, pens, and notebooks} for school.”

Better: “I need paper, pens, and notebooks for school.” (no brackets needed)

Curly Brackets in Mathematics

In mathematics, curly brackets have essential, well-defined functions. They’re part of the standard mathematical notation taught in schools worldwide.

Defining Sets

The most common use of curly brackets in mathematics is to define a set — a collection of distinct objects or numbers.

Example 1: A = {1, 2, 3, 4, 5}

Meaning: Set A contains the numbers 1 through 5.

Example 2: Vowels = {a, e, i, o, u}

Meaning: The set of vowels in English contains these five letters.

Example 3: B = {x | x is an even number between 1 and 10}

Meaning: Set B contains all even numbers from 1 to 10 (2, 4, 6, 8). The vertical line “|” means “such that.”

Order of Operations

In complex mathematical expressions, brackets are used to indicate which operations should be performed first. When multiple bracket types appear together, you work from the innermost to outermost: ( ), [ ], { }.

Example: 3 + { 4 × [2 + (5 – 1)] }

To solve this:

1. First, solve the parentheses: (5 – 1) = 4
2. Then, solve the square brackets: [2 + 4] = 6
3. Then, solve the curly brackets: 4 × 6 = 24
4. Finally, add: 3 + 24 = 27

Function Notation

In some mathematical contexts, curly brackets can denote the range or domain of a function — the set of input or output values.

Example: f(x) = {y | y = 2x + 1}

Meaning: The function f produces outputs (y values) by multiplying any input x by 2 and adding 1.

Curly Brackets in Programming

In programming languages such as C, C++, Java, C#, JavaScript, and many others, curly brackets are essential structural elements. They define code blocks and determine how programs execute.

Defining Code Blocks in Loops

In most programming languages, curly brackets enclose the statements that make up a loop. The loop executes the code inside the brackets repeatedly.

C / C++ example:

for (int i = 0; i < 10; i++) {
  printf(“%d\n”, i);
}

Explanation: The curly brackets enclose the printf statement. This statement executes 10 times as i counts from 0 to 9.

Defining Functions and Methods

Curly brackets define the body of a function — the code that runs when the function is called.

JavaScript example:

function greet(name) {
  console.log(“Hello, ” + name + “!”);
  return true;
}

Explanation: When greet() is called, the code inside the curly brackets executes.

Defining Objects and Data Structures

In languages like JavaScript and JSON (JavaScript Object Notation), curly brackets define objects — collections of key-value pairs.

JavaScript object example:

let person = {
  name: “John”,
  age: 30,
  city: “New York”
};

Explanation: This creates an object called “person” with three properties.

Defining Conditional Blocks

Curly brackets also enclose the code that runs if a condition is true.

Python example (note: Python often uses indentation instead of brackets):

if (temperature > 30) {
  console.log(“It’s hot!”);
} else {
  console.log(“It’s cool.”);
}

How to Type Curly Brackets on a Keyboard

On a standard QWERTY keyboard, curly brackets are located on the same keys as square brackets, accessed using the Shift key.

Bracket	Keyboard Combination	Key Location
Left curly bracket {	Shift + [	Top row, right side
Right curly bracket }	Shift + ]	Top row, right side

Example practice: Hold Shift and press the [ key to get {. Hold Shift and press the ] key to get }.

On non-English keyboards (QWERTY layouts used in different countries), the bracket keys may be in different locations, but the Shift + [ and Shift + ] combination usually still works.

Common Mistakes with Curly Brackets

✗ Incorrect: Please submit your essays {on time or you will lose points}.

✓ Correct: Please submit your essays on time, or you will lose points.

Why: Curly brackets are unnecessary in normal writing. Use a comma or em dash instead.

✗ Incorrect: I need { paper, pens, and ink } for the office.

✓ Correct: I need paper, pens, and ink for the office.

Why: Brackets add nothing here. In normal lists, avoid them entirely.

✗ Incorrect (Programming): for (int i = 0; i < 10; i++) { printf("%d", i);

✓ Correct (Programming): for (int i = 0; i < 10; i++) { printf("%d", i); }

Why: Missing closing bracket causes a syntax error.

Sample Dialogue: Understanding Brackets in Class

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