Comma Rules: The Complete Guide

Master the Most Used (and Misused) Punctuation Mark

Quick Answer

Use commas for: Lists, introductory phrases, joining independent clauses, non-essential info, and dates/addresses.

Don't use commas: Before "because" (usually), between subject and verb, or randomly for pauses.

Rule 1: Lists (Including the Oxford Comma)

Separate items in a list with commas.

  • I bought apples, oranges, and bananas. ✓
  • Red, white, and blue. ✓
  • The Oxford comma (before "and") is optional but recommended for clarity.
  • Without it: "I love my parents, Batman and Wonder Woman." (Are your parents superheroes?)
  • With it: "I love my parents, Batman, and Wonder Woman." (Clear!)

Rule 2: Introductory Phrases

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

  • However, I disagree. ✓
  • After the movie, we went home. ✓
  • If you're hungry, eat something. ✓
  • In 2020, everything changed. ✓
  • Running late, she skipped breakfast. ✓

Rule 3: Compound Sentences

Use a comma before a coordinating conjunction (and, but, or, so, yet) joining two independent clauses.

  • I wanted to go, but I was tired. ✓
  • She studied hard, and she passed. ✓
  • We can eat now, or we can wait. ✓
  • NOT: "I wanted to go, and eat." (not two independent clauses) ✗

Rule 4: Non-Essential Information

Set off non-essential (non-restrictive) information with commas.

  • My brother, who lives in Paris, is visiting. ✓ (extra info)
  • The book, which I bought yesterday, is amazing. ✓
  • But NO comma for essential info: "The brother who lives in Paris is visiting." (specifying which brother)

Comparison Chart

Use Comma ✓ No Comma ✗
In lists: "a, b, and c" Between two items: "a and b"
After intro phrases: "However, ..." After short intros (optional): "Then we left"
Before FANBOYS + independent clause Before FANBOYS + dependent clause
Non-essential info: ", which is great," Essential info: "that is great"
Dates: "July 4, 2024" Month/year only: "July 2024"

Common Mistakes & How to Avoid Them

❌ Incorrect:

"I went to the store, and bought milk."

✓ Correct:

"I went to the store and bought milk."

Why? "Bought milk" isn't an independent clause—no comma needed.
❌ Incorrect:

"The dog, barked loudly."

✓ Correct:

"The dog barked loudly."

Why? Never put a comma between subject and verb.
❌ Incorrect:

"I didn't go, because I was tired."

✓ Correct:

"I didn't go because I was tired."

Why? Usually no comma before "because" when it follows the main clause.

Quick Tips

💡 The Pause Myth

"Use a comma where you pause" is unreliable. Follow the rules instead.

✅ FANBOYS

For, And, Nor, But, Or, Yet, So. Comma before these only when joining independent clauses.

Frequently Asked Questions

Should I use the Oxford comma?

It's a style choice. Academic and professional writing often use it. Be consistent throughout your document.

Comma before "and" in dates?

"July 4, 2024" (comma after day). "July 2024" (no comma). "The event on July 4, 2024, was memorable" (comma after year too).

What's a comma splice?

Incorrectly joining two independent clauses with just a comma: "I ran, I won." Fix with: semicolon, period, or conjunction.

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