Whether to put a comma before “and” depends on what “and” is connecting. The two most common cases are lists and complete sentences.
1. Comma before “and” in a list
When listing three or more items, the comma before the final “and” is called the serial comma or Oxford comma.
With the Oxford comma:
- We bought apples, oranges, and bananas.
- The workshop covers planning, writing, and editing.
- She invited her parents, her manager, and her best friend.
Without the Oxford comma:
- We bought apples, oranges and bananas.
- The workshop covers planning, writing and editing.
Both styles may be acceptable, depending on the style guide being followed. American academic and book publishing often uses the Oxford comma, while some journalistic styles omit it. Whichever style you use, stay consistent.
Use the comma when leaving it out could create confusion:
- Clear: I’d like to thank my parents, my mentor, and my coach.
- Potentially confusing: I’d like to thank my parents, my mentor and my coach.
The second version might accidentally suggest that the mentor and the coach are the speaker’s parents.
2. Comma before “and” between complete sentences
Use a comma before “and” when it joins two independent clauses—two parts that could each stand alone as a sentence.
- The meeting ended, and everyone went home.
- I finished the report, and my colleague reviewed it.
- The rain stopped, and the children returned outside.
A quick test is to separate the clauses:
The meeting ended. Everyone went home.
Because both are complete sentences, the comma is appropriate.
3. No comma with a compound predicate
Do not normally use a comma when “and” connects two actions performed by the same subject.
- She opened the door and walked inside.
- We reviewed the proposal and approved it.
- The dog ran across the yard and jumped over the fence.
In each example, the subject is not repeated. Compare:
- She opened the door and walked inside.
- She opened the door, and she walked inside.
The second version has two complete clauses, so it takes a comma.
4. Comma for a deliberate pause or contrast
A comma may sometimes appear before “and” for emphasis, surprise, or a strong pause:
- He promised to arrive early, and then showed up two hours late.
- She tried again, and again, and again.
This is a stylistic use rather than the standard grammatical rule.
Quick rule
Use a comma before “and”:
- before the last item in a list, if using the Oxford comma;
- when joining two complete sentences;
- when needed to prevent ambiguity or create deliberate emphasis.
Usually omit it when “and” simply connects two words, phrases, or actions:
- tea and coffee
- calm and confident
- packed her bag and left the house