Comma Rules
A complete A2 guide to using commas in English — items in a series, joining clauses with FANBOYS conjunctions, introductory phrases, non-essential information, and the most common comma mistakes.
What a Comma Does
A comma (,) tells the reader to pause briefly. It separates parts of a sentence so the meaning is clear.
There are three main uses for a comma in English:
| Use | Example |
|---|---|
| A. Separate items in a list | I bought apples, bread, and cheese. |
| B. Join two complete sentences with a conjunction | I was tired, but I kept working. |
| C. Set off introductory or extra information | When you arrive, call me. |
This lesson covers all three, plus a few special uses and common mistakes.
A. Items in a Series
Use a comma to separate three or more items in a list. The items can be nouns, adjectives, or verbs.
I had eggs, toast, and coffee for breakfast.
She is kind, smart, and funny.
He runs, swims, and cycles every week.
The Oxford Comma
The comma before and (or or) at the end of a list — apples, bread, and cheese — is called the Oxford comma (or serial comma). Some style guides use it, others leave it out:
| With Oxford comma | Without Oxford comma |
|---|---|
red, white, and blue | red, white and blue |
Both are accepted. We recommend using it for clarity. Be consistent within one piece of writing.
Coordinate vs. Non-Coordinate Adjectives
Use commas between coordinate adjectives (adjectives of equal weight that you could re-order or join with and).
It was a long, boring lecture. (= a boring, long lecture — both orders work)
Do not use a comma between non-coordinate adjectives (where order is fixed and you cannot insert and).
She has a small black dog. (a small, black dog sounds wrong; black, small is wrong)
Quick test: if you can swap the adjectives or add
and, use a comma.
B. Joining Two Sentences (FANBOYS)
When you join two complete sentences (independent clauses) with a coordinating conjunction, put a comma before the conjunction.
The seven coordinating conjunctions are easy to remember as FANBOYS:
| F | A | N | B | O | Y | S |
|---|---|---|---|---|---|---|
| for | and | nor | but | or | yet | so |
I wanted to go, but I was too tired.
We can stay home, or we can go out.
The bus was late, so I walked.
She did not study, yet she passed the test.
Don’t Use a Comma Alone (Comma Splice)
A common mistake is joining two sentences with only a comma — no conjunction. This is called a comma splice.
| Wrong (comma splice) | Right |
|---|---|
I was tired, I went home. | I was tired, so I went home. |
It is cold, take a jacket. | It is cold. Take a jacket. |
Fix a comma splice three ways: add a conjunction, use a period (full stop), or use a semicolon.
Don’t Use a Comma for a Compound Verb
If a single subject does two actions joined by and, no comma is needed — there is only one sentence, not two.
| Wrong | Right |
|---|---|
She opened the door, and walked in. | She opened the door and walked in. |
He laughed, and clapped his hands. | He laughed and clapped his hands. |
C. Introductory and Extra Information
Introductory Phrases
When a sentence starts with an introductory word, phrase, or clause, put a comma after it.
First, mix the eggs and the milk.
In the morning, I drink coffee.
When you finish, please call me.
After the rain stopped, we went outside.
If the same information comes at the end of the sentence, you usually do not need a comma.
| Comma needed | No comma |
|---|---|
When you finish, please call me. | Please call me when you finish. |
After dinner, we watched a film. | We watched a film after dinner. |
Non-Essential Information
Use two commas to set off extra information that you could remove without changing the basic meaning.
My brother, who lives in Paris, is a chef.
(The basic sentence is My brother is a chef. The middle part is extra.)
The teacher, Mrs. Lee, is from Korea.
Tokyo, the capital of Japan, has 14 million people.
If the information is essential to identify which person or thing you mean, do not use commas.
| Non-essential (use commas) | Essential (no commas) |
|---|---|
My only sister, who lives in Paris, is a chef. (you only have one sister) | My sister who lives in Paris is a chef. (you have several sisters; you mean the Paris one) |
D. Other Common Uses
| Where | Example |
|---|---|
| Direct address (talking to someone) | Anna, can you help me? / Thanks, mom. |
| Tag questions | You are coming, aren't you? |
| Dates | I was born on May 7, 1990. |
| Cities and countries | She lives in Lima, Peru. |
| Large numbers (every 3 digits) | 2,500 / 25,000 / 2,500,000 |
| Quotations | He said, "I am hungry." |
| Letter openings (informal) | Dear Sam, |
Common Mistakes
| Mistake | Fix | Why |
|---|---|---|
I went home, I was tired. | I went home because I was tired. / I went home. I was tired. | A comma alone cannot join two sentences (comma splice). |
Maria, and Tom went out. | Maria and Tom went out. | Don’t put a comma between two subjects joined by and. |
He is a kind, careful, driver. | He is a kind, careful driver. | Don’t put a comma between the last adjective and the noun. |
I really, like coffee. | I really like coffee. | Don’t put a comma between an adverb and the verb it modifies. |
My friend, who lives in Lima is a doctor. | My friend, who lives in Lima, is a doctor. | Use two commas around non-essential information, not one. |
Approximately 30000 people came. | Approximately 30,000 people came. | Use a comma every three digits in large numbers. |
Practice: Exercises
Which sentence uses commas correctly for items in a series?
Summary
A comma has three main jobs: separate items in a list, join two sentences with a FANBOYS conjunction (for, and, nor, but, or, yet, so), and set off introductory or extra information.
The biggest mistakes to avoid: a comma splice (joining two sentences with only a comma), a comma between two subjects joined by and, and forgetting the second comma around non-essential information.
When in doubt, ask: would I pause here when reading aloud? If yes, a comma is probably right. If no, leave it out — modern English uses fewer commas than older writing.