Writing commas

Would you put a comma before "and" in a list? And what about before "because" or "which"?

The comma is one of the most common punctuation marks in English — and one of the most misused. Commas are not placed randomly; they follow sentence structure and help the reader understand meaning.

The serial comma (Oxford comma)

In a list of three or more items, you can use a comma before the final and:

I bought apples, bananas, and oranges.

This is called the serial (Oxford) comma. It is optional, but it helps avoid confusion.

I thanked my parents, Mother Teresa and the Pope
→ unclear

I thanked my parents, Mother Teresa, and the Pope
→ clear

Comma with coordinating conjunctions (FANBOYS)

When joining two independent clauses with a conjunction (for, and, nor, but, or, yet, so), use a comma:

I wanted to go, but it started to rain.

If the second part is short and shares the same subject, the comma may be omitted:

I went home and had dinner.

Comma with subordinating conjunctions

Words like because, although, if, when introduce dependent clauses.

If the dependent clause comes first, use a comma:

Although it was raining, we went outside.

If it comes second, usually no comma:

We went outside although it was raining.

Comma with "which" and "that"

This is a key distinction:

Non-defining clause (extra information):
use which + commas

The book, which I bought yesterday, is excellent.

Defining clause (essential information):
use that + no commas

The book that I bought yesterday is excellent.

Commas change meaning here.

Comma after introductory elements

Use a comma after introductory words, phrases, or clauses:

In the morning, I drink coffee.
However, the result was different.
Because it was late, we left.

Commas for extra information

Use commas to separate non-essential (extra) information:

My brother, who lives in Paris, is a chef.

If you remove the extra part, the main meaning stays the same.

Common mistakes

❌ Comma splice:
It was late, we went home.

✔ Fix:
It was late, so we went home.
It was late. We went home.

❌ Comma between subject and verb:
The tall boy, ran quickly.

✔ Correct:
The tall boy ran quickly.

Comma before "because"?

Usually NO comma:

I left because I was tired.

Sometimes YES (to clarify meaning):

I didn’t leave, because I was tired.
(meaning: the reason was not tiredness)

How to decide

Ask:

• Am I joining two complete sentences?
• Is this extra information or essential?
• Does the comma change meaning?

Commas are about clarity, not decoration.

Key idea

Commas show structure and meaning.

Used correctly, they make writing easier to read and understand.