Grammar
Commas: separate ideas without overusing them
A comma can make a long sentence easier to read, but it cannot repair every pause you hear. Compare these sentences: After lunch, we reviewed the proposal. We reviewed the proposal after lunch. Both are clear because the comma follows an opening part, not an arbitrary pause.
Place commas where they separate list items, joined complete ideas, introductory parts, direct address, or extra information, and leave them out where they break a sentence's main structure.
Read and practice
Read the examples and try the written questions in this guide. Listening recordings are not available for this lesson yet.
Try the written questions
After lunch, we reviewed the proposal. /ˈæf.tɚ lʌntʃ, wi rɪˈvjuːd ðə prəˈpoʊ.zəl/
The short answer
Use a comma when it helps readers see the parts of a sentence. Common places are between list items, before a coordinating conjunction that joins two complete ideas, after an introductory part, around extra information, and with a person's name when you speak directly to that person.
The lights went out, but the meeting continued.
Why it works: The comma comes before but because the words on both sides can stand as complete sentences.
5 more examples
-
We packed water, fruit, and sandwiches.
The commas separate three items in one list.
Not this:We packed water,
fruit and sandwiches. What changes: Some styles omit the final comma before and. Follow the punctuation style your course, workplace, or publication uses. -
I finished the notes, and I emailed them to the group.
I finished the notes and I emailed them to the group are both complete ideas, so the comma comes before and.
Not this:I finished the
notes, I emailedthem to the group. What changes: A comma alone should not join two complete sentences. Add a conjunction, use a period, or revise the sentence. -
Before the class began, we checked the projector.
The opening clause tells the reader when the action happened. The comma marks the end of that opening part.
Not this:We checked the projector
before the class began. What changes: The same time phrase follows the main sentence here, so it does not need a comma. -
The train, which was already full, left on time.
The clause adds information about the train. The sentence still identifies the train without that detail.
Not this:Passengers
who had ticketsentered first. What changes: The clause identifies which passengers entered first, so it is not set off with commas. -
Nina, could you check the address?
The comma marks Nina as the person being spoken to directly.
Not this:Could you check the address
, Nina? What changes: A name at the end of direct address also takes a comma.
Read the full guide
First, find the main subject and verb. Do not separate them with a comma. Then look for a list, an opening part, an added detail, or two full ideas joined by and, but, so, or another coordinating conjunction. A comma has a job in these patterns. If you cannot name that job, leave the comma out until you can check the sentence again.
Separate items in a list
Use commas to separate three or more items when they have the same job in a list. The reader can then see where each item begins and ends. In many styles, a final comma appears before and or or. Other styles leave it out. Choose the required style and use it consistently.
We packed water, fruit, and sandwiches.
Water, fruit, and sandwiches are three things that the group packed.
Which words are the list items in the sentence?
The items are water, fruit, and sandwiches.
Join complete ideas carefully
A comma can come before and, but, so, yet, or another coordinating conjunction when the conjunction joins two complete ideas. A complete idea has its own subject and verb. If the second part cannot stand by itself, it usually does not need this comma.
I finished the notes, and I emailed them to the group.
Both I finished the notes and I emailed them to the group can be complete sentences.
Why is there a comma before and?
The comma comes before and because it joins two complete ideas.
Mark an introductory part
An opening clause or a clear opening phrase prepares the reader for the main sentence. Put a comma after that opening part, especially when it is long enough to make the boundary useful. When the same words come after the main sentence, a comma is often unnecessary.
Before the class began, we checked the projector.
Before the class began is the opening part. We checked the projector is the main sentence.
Where does the opening part end?
It ends after began, so the comma goes there.
Set off extra information
Use a pair of commas when words add information about a person or thing that the reader can already identify. Do not use commas when the words are needed to identify which person or thing you mean. Removing the extra words is a useful check: if the main meaning still identifies the person or thing, commas may be appropriate.
The train, which was already full, left on time.
Which was already full adds a fact about the train; it does not tell the reader which train is meant.
What happens if you remove which was already full?
The main sentence remains: The train left on time.
Use commas when speaking to someone
A comma separates a name from the rest of a sentence when you speak directly to that person. The name can come at the beginning, middle, or end. This pattern helps the reader see that the name is an address, not the subject of the sentence.
Nina, could you check the address?
Nina is the listener. The subject of could you check is you.
How do you punctuate a name at the end of direct address?
Put a comma before it: Could you check the address, Nina?
Do not add a comma for every pause
A spoken pause is not a complete punctuation rule. Do not put a comma between a subject and its verb, between a verb and its object, or after a coordinating conjunction. A comma alone also cannot join two complete sentences. When a sentence feels crowded, use a period or revise the wording instead of adding commas at random.
The manager approved the plan.
The manager is the subject, and approved is its verb, so a comma does not belong between them.
Can a comma by itself join The manager approved the plan and The team began work?
No. Use a period, a semicolon when appropriate, or a comma plus a coordinating conjunction.
Before you go
Remember this
Use commas to separate list items, to introduce a second complete idea after a coordinating conjunction, and to mark opening parts, extra detail, and direct address. Check the sentence's main subject and verb before you punctuate. If a comma breaks that core structure or joins two complete sentences by itself, change the punctuation or rewrite the sentence.
Practice with the written examples
You can practice with the written questions in the Learn tab. Each answer includes an explanation.
Try the written questionsListening test not available yet
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Try the written questionsQuestions about "Commas: separate ideas without overusing them"
When should I use commas in a list?
Use commas to separate three or more items that have the same job in a list. For example, write water, fruit, and sandwiches. Some style guides omit the final comma before and, so follow the style required for your course, workplace, or publication.
We packed water, fruit and sandwiches.
Do I need a comma before and or but?
Use a comma before and or but when the word joins two complete ideas. Each side needs its own subject and verb. Do not add the comma just because the sentence contains and or but; a short second phrase may not need it.
I finished the notes, and I emailed them to the group.
Why is a comma used after an introductory phrase?
A comma after an introductory phrase or clause shows where the opening information ends and the main sentence begins. It helps readers follow the order of the ideas, especially when the opening part gives time, reason, condition, or contrast.
I finished the notes, I emailed them to the group.
How do commas change extra information in a sentence?
Commas can show that words add extra information about a person or thing that is already clear. Without commas, a clause may identify exactly which person or thing you mean. Check whether the main sentence still identifies the person or thing after you remove the added words.
Before the class began, we checked the projector.
Where should I not put a comma?
Do not normally put a comma between a subject and its verb or between a verb and its object. A comma alone also cannot join two complete sentences. Use a period, a coordinating conjunction with a comma, or a different sentence structure when needed.
We checked the projector before the class began.