Commas can separate items, mark a clause boundary, or set off added information. This lesson covers six common situations. Read the examples, then try the short practice beneath each section.
Different styles, shared principles
Comma conventions vary: some styles favour fuller punctuation, while others use fewer commas when the meaning remains clear.
This guide focuses on clear, standard English for school and academic writing. It recommends commas that make sentence structure easier to follow.
Some choices are matters of style, such as the Oxford comma or a comma after a short introduction. Others change meaning. Use structure and meaning—not just pauses—to decide.
In the correction cards: reasonable alternatives are accepted and explained. Keep the meaning given in the context, and use paired commas together. If your assignment requires a particular style, follow it consistently.
1. Items in a list
Use commas to separate three or more items. The items can be individual words or longer phrases.
Example: commas separate the list items
Bring a notebook, a pen, and your reading book.
The commas separate three things to bring. The comma before and is called the serial or Oxford comma.
Example: the final comma is optional
Bring a notebook, a pen and your reading book.
This version is also acceptable. Some styles use the final comma and others leave it out. Use it when it helps prevent confusion.
Two items usually need only and: Bring a notebook and a pen. You do not need a comma just because the list contains and.
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2. Introductory clauses
A clause beginning with a word such as although, because, when, or if can come before the main statement. This guide recommends a comma at the end of that introductory clause. Some styles omit it after a short, clear introduction; the correction cards accept that lighter punctuation where appropriate.
Example: comma after the introductory clause
Although the rain had stopped, the paths were still wet.
Although the rain had stopped is a dependent clause. The comma marks where the main clause begins.
Example: no comma needed
The paths were still wet although the rain had stopped.
When the main clause comes first, this sentence does not normally need a comma before although.
Short introductory time phrases can allow a choice: On Monday we met and On Monday, we met. Longer introductions often benefit from a comma. In these exercises, focus on clear introductory clauses.
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3. Joining complete clauses
When you connect two independent clauses with and, but, or so, a comma normally comes before the conjunction. An independent clause can stand alone as a sentence.
Example: comma before the conjunction
Maya revised her essay, but she forgot to save it.
Maya revised her essay and she forgot to save it are both complete clauses. The comma comes before but.
Example: no comma needed
Maya revised her essay and saved it.
The verbs revised and saved share the subject Maya. The second part is not an independent clause, so a comma is usually unnecessary.
Other coordinating conjunctions include or, nor, for, and yet. Some styles omit the comma between very short, closely connected clauses. For longer clauses, the comma helps readers see the boundary.
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4. Extra information
Use a pair of commas around added information in the middle of a sentence. The commas signal that this information is supplementary, rather than identifying which person or thing you mean.
Example: commas around extra information
Jerry, who lives nearby, joined us.
Jerry is already identified by name. Who lives nearby adds information. Both commas are needed because the main sentence continues.
Example: no commas around identifying information
The students who finished early left the room.
Who finished early identifies which students left. With no commas, the sentence does not say that all the students finished early.
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5. Speaking directly to someone
Separate the name of the person you are addressing from the rest of the sentence. The name can appear at the beginning, middle, or end.
Example: comma for direct address
Jerry, could you help me?
The speaker is talking to Jerry. The comma separates his name from the question.
Examples: commas for direct address
Could you, Jerry, help me?
Could you help me, Jerry?
Use two commas when the name interrupts the sentence, and one when it comes at the end.
Compare Jerry helped me. Here Jerry is the subject: the sentence describes what he did. There is no comma after his name.
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6. Where a comma does not belong
A comma does not normally separate a subject from its verb or a verb from its object. A comma alone also cannot join two independent clauses in standard academic writing.
Example: no comma between subject and verb
Correct: The students in the back row finished the task.
Wrong: The students in the back row, finished the task.
The whole subject is The students in the back row. Do not put a comma between row and finished.
Example: no comma between verb and object
Correct: Maya checked the answer.
Wrong: Maya, checked the answer.
Wrong: Maya checked, the answer.
Do not separate checked from its object, the answer, with a comma.
Original error
The library was closed, we went home.
This is a comma splice: The library was closed and we went home can each stand alone. A comma alone does not create a suitable boundary.
Possible repairs
The library was closed, so we went home.
The library was closed. We went home.
A comma with so expresses the result. A full stop also repairs the boundary. A semicolon is another possibility.
Use sentence structure and meaning to decide where a comma belongs. A pause while reading aloud can be a clue, but it is not a rule by itself.
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A quick check before you finish
Ask what job each comma does. Does it separate list items, introduce the main clause, join clauses with a conjunction, mark extra information, or separate a person’s name in direct address?
Check for missing pairs around extra information, and check that a comma has not split a subject from its verb or joined two complete clauses on its own.
Some comma choices depend on style or intended meaning. The exercises focus on the stated context and recognise optional choices rather than treating them as universal errors.
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