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HomeBlogsOET Grammar and Punctuation: Commas
OET Grammar and Punctuation: Commas

Healthcare professionals writing on paper

A consistent challenge in any language proficiency test is punctuation. In particular, the comma. It's small, it's mighty, and when used correctly, it can significantly enhance your written communication.

Let's demystify this little punctuation mark and help you ace your OET Writing test. There are a LOT of rules about when to use commas, but here are five of the most useful ones to know:


Five comma rules

Rule 1: use a comma to separate independent clauses

Commas are used to separate two independent clauses* when they are joined by coordinating conjunctions like 'and', 'but', 'or', 'so'. There are only seven coordinating conjunctions (for, and, nor, but, or, yet, so) and you can remember them with this acronym: FANBOYS. The most commonly used ones are ‘and’, ‘but’ and ‘so’.

*An independent clause is a group of words that can stand alone as a sentence as it expresses a full thought.

Example: "Mr Kymont was recommended physiotherapy, and he will begin his sessions next week."


Rule 2: use a comma after an introductory element

Often, a sentence will begin with an introductory word, phrase, or clause. In such cases, use a comma after the introductory element to set it off from the rest of the sentence.

Example: "During his last consultation, Mr Smith reported improved mobility after his knee replacement surgery."


Rule 3: use commas to separate elements in a series

When listing three or more items, use commas to separate each item. The final comma before the conjunction (usually 'and' or 'or') is known as the Oxford comma.

Example: "I have advised Ms Davis to eat a balanced diet, increase her physical activity, and attend regular check-ups for monitoring her diabetes."


Rule 4: use a comma to set off non-essential information

A non-essential element is a word, phrase, or clause that is not essential to the meaning of the sentence. Commas are used to set off non-essential elements.

Example: "Ms Ferrago, despite experiencing mild discomfort post-surgery, is recovering well and eager to return home."


Rule 5: use a comma after a dependent clause that begins a sentence

A dependent clause at the beginning of a sentence is often followed by a comma. This is to indicate the end of the dependent clause and the start of the independent clause, which is the main point of the sentence. You will often see this comma when a sentence starts with a subordinating conjunction such as ‘although’, ‘if’, ‘when’, ‘while’, ‘after’, ‘until’ and ‘because’.

Example: "Although Mr Johnson has made some improvement in his health, he still requires ongoing monitoring of his blood pressure."


Three common errors

Here are some of the most common errors people make with commas (and the corrected sentences).

Error 1: joining two sentences with a comma only (aka a ‘comma splice’)

When two sentences are joined with only a comma, it's wrong. We can use 'and', a semicolon, or make two sentences.

Incorrect: "Dr Lee checked the patient's lab results, he didn't find anything wrong."

Correct: "Dr Lee checked the patient's lab results and didn't find anything wrong."


Error 2: Using a comma with a defining relative clause

A defining relative clause is a clause that you can't get rid of because it specifically defines some part of the sentence. Don't separate a defining relative clause from the rest of the sentence with commas.

Incorrect: "The patient who has type 2 diabetes, should continue taking his insulin medication."

Correct: "The patient who has type 2 diabetes should continue taking his insulin medication."


Error 3: Using an unnecessary comma with two actions

When the same person or thing is doing two things, you don't need a comma.*

Incorrect: "Mrs Brown has a check-up next week, and also needs more tests."

Correct: "Mrs Brown has a check-up next week and also needs more tests."


*As in Rule #1 above, if you have two complete sentences and a coordinating conjunction, you should use a comma.

Correct: “Mrs Brown has a check-up next week, and she also needs more tests.”


Remember, correct comma usage makes your writing clearer and easier to read. It also shows a high level of English proficiency, which can help boost your OET writing score. Keep practising, look for how commas are used in expert writing, and avoid the common errors above for a successful OET experience.

Good luck!