Overview
Commas are the most frequently used punctuation mark in English. They separate items in a list, join independent clauses after a coordinating conjunction, follow introductory phrases, and set off non-defining clauses. Incorrect comma use is one of the most common writing errors.
When to Use Commas
- ListsI need eggs, milk, bread, and butter.
- Before CCShe was tired, but she kept going.
- After IntroAfter the storm, the streets were flooded.
- Non-definingMy sister, who lives in Paris, visited last week.
Oxford Comma
- The Oxford comma = comma before 'and' in a list.
- Without: I love my parents, Madonna and God (ambiguous)
- With: I love my parents, Madonna, and God (clear)
- British English: often omitted · American English: often kept
Common Mistakes
- ❌ Comma splice: I was tired, I went home → ✅ use semicolon or conjunction
- ❌ She said, that she was coming → ✅ no comma before 'that' in reported speech
- ❌ A tall, dark man walked in → ✅ only comma between coordinate adjectives
When to use
Lists
Pack your coat, hat, gloves, and boots.
Joining clauses
I wanted to go, but it was raining.
Introductions
In summary, the plan was successful.
Extra info
James, my oldest friend, called last night.