# How to use a colon

Canonical: https://duckyhelper.com/learn/grammar/colons/
Updated: 2026-10-01

Use a colon after a complete sentence to introduce a list, an example, an explanation or a quotation: I need three things: a pen, a ruler and tape. The words before the colon must be able to stand alone as a sentence, so never put a colon right after are, include or such as. Colons also separate hours from minutes (3:15) and a title from its subtitle.

## The main rule

Think of a colon as an arrow that says *here it is*. What comes before the arrow must be a complete sentence. What comes after it delivers what the sentence promised.

| Use | Wrong | Right | Why |
| --- | --- | --- | --- |
| Introduce a list | *My favorite subjects are: math, art, and history.* | *I have three favorite subjects: math, art, and history.* | *My favorite subjects are* is not complete. *I have three favorite subjects* is. |
| Introduce an explanation | *There was only one problem, the bus never came.* (a comma splice) | *There was only one problem: the bus never came.* | The second part explains the *one problem* promised in the first. |
| Introduce an example or a single item | *She had one goal; to finish the race.* | *She had one goal: to finish the race.* | *To finish the race* is not a sentence, so a semicolon cannot come before it. |
| Never after *such as* or *including* | *Bring snacks such as: apples and crackers.* | *Bring snacks such as apples and crackers.* | *Such as* already introduces the list. No colon needed. |

- **Time:** *The bus leaves at 7:45.*
- **Titles and subtitles:** *Star Wars: A New Hope*.
- **Ratios:** *a ratio of 2:1*.

> **Note: Capital letter after a colon?**
>
> Style guides disagree. APA and AP capitalize the first word after a colon when it starts a complete sentence. Chicago and MLA usually keep it lowercase unless it is a proper noun. Follow your teacher's style. Either way, a list or phrase after a colon starts in lowercase.

## Worked examples

**Example 1: a colon after are**

Problem: *The ingredients are: flour, water, and salt.*

1. Read the words before the colon alone: *The ingredients are.* That is not a complete sentence.
2. Option one: remove the colon, since the list finishes the sentence.
3. Option two: rewrite so a complete sentence comes first, then keep the colon.

Answer: *The ingredients are flour, water, and salt.* or *The recipe needs three ingredients: flour, water, and salt.*

**Example 2: colon or semicolon?**

Problem: *The coach gave us one piece of advice ___ patience.*

1. Is the first part complete? *The coach gave us one piece of advice.* Yes.
2. Is the second part a complete sentence? *Patience* is one word, not a sentence. So a semicolon is out.
3. The second part names the advice the first part promised. That is a colon's job.

Answer: *The coach gave us one piece of advice: patience.*

## Common mistakes and fixes

| Mistake | Fix |
| --- | --- |
| Colon right after a verb (*are*, *include*, *is*) | Remove it, or add words so the first part is complete: *includes the following:* |
| Colon after *such as*, *including* or *for example* | Drop the colon. Those words already introduce the list. |
| Using a semicolon before a list | Lists after a complete sentence take a colon. Semicolons join sentences. |
| More than one colon in a sentence | Use one colon per sentence. Rewrite if you need two. |

## Practice

**Five colon questions**

1. Which sentence uses a colon correctly?
   A. The two things to bring are: a pencil and a calculator.
   B. Bring: a pencil and a calculator.
   C. Bring two things: a pencil and a calculator.
   D. Bring two things such as: a pencil and a calculator.

   Answer: Bring two things: a pencil and a calculator.. *Bring two things* is a complete sentence (a command with *you* understood), so a colon can follow it. In the others, the words before the colon are not complete: *are*, *Bring* and *such as* all need what comes after.

2. Which sentence is punctuated correctly?
   A. There was only one: problem the bus never came.
   B. There was only one problem: the bus never came.
   C. There was: only one problem the bus never came.
   D. There was only one problem the bus: never came.

   Answer: There was only one problem: the bus never came.. The colon follows the complete sentence *There was only one problem* and introduces the explanation. The other choices put the colon in the middle of a phrase.

3. Which sentence uses a colon incorrectly?
   A. The meeting starts at 3:30.
   B. He gave one reason: he was tired.
   C. The recipe includes: flour, sugar, and eggs.
   D. I have one rule: be on time.

   Answer: The recipe includes: flour, sugar, and eggs.. *The recipe includes* is not complete without its object, so no colon belongs there. The others use a colon for time, after a complete sentence before an explanation, and after a complete sentence before a rule.

4. Which punctuation belongs in the blank? *We need three things ___ a map, a flashlight, and water.*
   A. a colon after need instead (We need: three things a map...)
   B. a semicolon (;)
   C. no punctuation
   D. a colon (:)

   Answer: a colon (:). *We need three things* is a complete sentence, and a list follows, so a colon goes in the blank. A semicolon must be followed by a full sentence, no punctuation runs the list into *things*, and a colon after *need* breaks the complete-sentence rule.

5. How is the time written correctly in US English?
   A. The train leaves at 7:45.
   B. The train leaves at 7;45.
   C. The train leaves at 7,45.
   D. The train leaves at 745 o'clock.

   Answer: The train leaves at 7:45.. In US English a colon separates hours from minutes. Semicolons and commas are not used for time, and *o'clock* is only for whole hours.

## Frequently asked questions

### Can a colon join two complete sentences?

Yes, when the second sentence explains or expands the first: *I knew one thing for sure: we were lost.* If the two sentences are simply related, a [semicolon](https://duckyhelper.com/learn/grammar/semicolons/) or a period is the better choice.

### Do I use a colon or a comma before a quotation?

After a verb like *said* or *asked*, a comma is the usual choice: *She said, "Let's go."* Use a colon when a complete sentence introduces the quotation: *She repeated her favorite line: "Let's go."*

### Is it wrong to put a colon after includes?

In standard writing, yes, because *includes* needs its object to finish the sentence. Write *The kit includes a map and a compass* with no colon, or *The kit includes the following: a map and a compass*, where *the following* completes the sentence first.

## Sources

- [Purdue OWL, Semicolons, Colons, and Parentheses](https://owl.purdue.edu/owl/multilingual/multilingual_students/punctuation/semicolons_colons_and_parentheses.html), accessed 2026-10-01
- [Purdue OWL, Punctuation Introduction](https://owl.purdue.edu/owl/general_writing/punctuation/index.html), accessed 2026-10-01

## Related

- [When to use a semicolon](https://duckyhelper.com/learn/grammar/semicolons/)
- [Comma rules](https://duckyhelper.com/learn/grammar/commas/)
- [SAT punctuation: Boundaries questions](https://duckyhelper.com/learn/sat-reading-writing/boundaries-punctuation/)
- [Grammar study guides](https://duckyhelper.com/learn/grammar/)

## Try asking Ducky

- "Check every colon in my essay and tell me if the part before it is a complete sentence."
- "Is this a colon or a semicolon spot? Let me guess first."
- "Give me five sentences where I have to decide between a colon, a semicolon and nothing."

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