A comma is a breath, not a full stop
Here is a sentence that appears in almost every IELTS essay: "Traffic is bad, many people arrive late." It looks fine. It is a grammar error. A comma is a small pause inside one sentence. It is not strong enough to hold two complete sentences together. Most students do this five or six times on one page without noticing, and every one of them counts against accuracy.
The two-second test
Cover the comma with your finger. Look at what is on each side. Can both halves stand alone as a full sentence, each with its own subject and its own verb? If yes, a comma alone cannot join them. That is the whole test, and you can run it on any sentence you are unsure about, in the exam, in under two seconds.
4 ways to fix it
1Use a period
Traffic is bad. Many people arrive late. Always correct, always safe. If you are short of time in the exam, this is the fix to reach for.
2Add and, but, or so
Traffic is bad, so many people arrive late. The comma stays, and the little joining word does the work it could not do alone.
3Add because, although, or while
Because traffic is bad, many people arrive late. This is the best fix of the four. It repairs the punctuation and it builds a complex sentence, which your grammar score is actively looking for.
4Use a semicolon
Traffic is bad; many people arrive late. Correct, and it looks confident. Use it once or twice at most, and only when the two ideas are closely linked.
4 more comma habits worth fixing
However cannot join two sentences
✕The service is cheap, however it is slow.
✓The service is cheap. However, it is slow.
However is not a joining word like "but". It is a signal that starts a new sentence. Write a period before it and a comma after it, and this error disappears for good.
A missing comma after an opening clause
✕Although the policy is popular it is expensive.
✓Although the policy is popular, it is expensive.
When a sentence opens with although, because, if, while or when, put a comma where that first part ends. Without it, the reader has to go back and re-read.
A comma between the subject and its verb
✕Students who work part time, often struggle to keep up.
✓Students who work part time often struggle to keep up.
Never separate the doer from the action. The sentence has one subject and one verb, so nothing goes between them, however long the subject is.
A run-on with no comma at all
✕Many families cannot afford housing prices keep rising.
✓Many families cannot afford housing, because prices keep rising.
This one is harder to spot than a comma splice, because there is nothing there to notice. Read your essay out loud in your head. Where you take a breath, check what is holding the two halves together.
Why this is worth ten minutes of your week
Punctuation is not a separate score in IELTS. It sits inside Grammatical Range and Accuracy, next to your tenses and your sentence structures. So a page with six comma splices reads as a page with six grammar errors, even if every verb is perfect. It is also one of the few errors you can remove completely, because it is one rule, not a feel for the language. Learn the test, use it on your next three essays, and it becomes automatic.
Read next
More grammar that moves the number: a, an, the: the three smallest words that cost the most marks and 6 mistakes that make your IELTS score drop fast.
Count your own commas
You will not find these by re-reading, because your eye reads the meaning, not the punctuation. Write your next essay in VoyaLang and look at the correction list. Every comma splice, missing comma and run-on is marked in the sentence you actually wrote, so you can see how often you do it and which pattern is yours. Most students are surprised by the number. Create a free account and check your next essay in about a minute.
