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.
Worked examples
Example 1: a colon after are
Problem The ingredients are: flour, water, and salt.
- Read the words before the colon alone: The ingredients are. That is not a complete sentence.
- Option one: remove the colon, since the list finishes the sentence.
- 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.
- Is the first part complete? The coach gave us one piece of advice. Yes.
- Is the second part a complete sentence? Patience is one word, not a sentence. So a semicolon is out.
- 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
Which sentence uses a colon correctly?
- The two things to bring are: a pencil and a calculator.
- Bring: a pencil and a calculator.
- Bring two things: a pencil and a calculator.
- Bring two things such as: a pencil and a calculator.
Show answer
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.
Which sentence is punctuated correctly?
- There was only one: problem the bus never came.
- There was only one problem: the bus never came.
- There was: only one problem the bus never came.
- There was only one problem the bus: never came.
Show answer
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.
Which sentence uses a colon incorrectly?
- The meeting starts at 3:30.
- He gave one reason: he was tired.
- The recipe includes: flour, sugar, and eggs.
- I have one rule: be on time.
Show answer
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.
Which punctuation belongs in the blank? We need three things ___ a map, a flashlight, and water.
- a colon after need instead (We need: three things a map...)
- a semicolon (;)
- no punctuation
- a colon (:)
Show answer
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.
How is the time written correctly in US English?
- The train leaves at 7:45.
- The train leaves at 7;45.
- The train leaves at 7,45.
- The train leaves at 745 o'clock.
Show answer
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 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, accessed October 1, 2026
- Purdue OWL, Punctuation Introduction, accessed October 1, 2026
