Punctuation and sentence boundaries
Stop run-on sentences and comma splices — the errors that blur your meaning.
Why it matters
At Band 7 the descriptor says 'grammar and punctuation are generally well controlled'. Comma splices and run-ons are the most common punctuation errors in IELTS scripts, and they also make arguments harder to follow.
The rules
Two independent clauses need a full stop, a semicolon, or a conjunction.
Prices rose; demand fell. / Prices rose, so demand fell.
Put a comma after an introductory clause or linker.
However, this is not always true.
Non-defining relative clauses go between commas.
Lagos, which is Nigeria's largest city, is growing fast.
No comma before a defining clause or between subject and verb.
People who exercise live longer.
Model sentences
- Cars are convenient; however, they are a major source of urban pollution.
- In my view, the benefits clearly outweigh the drawbacks.
- The policy, which was introduced in 2018, has cut emissions by a fifth.
Common mistakes
Incorrect: Technology is useful, it saves time.
Correct: Technology is useful because it saves time. / …useful; it saves time.
A comma alone can't join two sentences.
Incorrect: Many people believe, that it is wrong.
Correct: Many people believe that it is wrong.
No comma before a 'that' clause.
Incorrect: The man, who lives next door, is a doctor. (if identifying which man)
Correct: The man who lives next door is a doctor.
Defining clauses take no commas.
Band tip
Check yourself
Fix: 'Some students work part-time, this affects their grades.'
Some students work part-time, which affects their grades. / …part-time; this affects their grades.
Add punctuation: 'nevertheless the plan was approved'
Nevertheless, the plan was approved.
Fix: 'Children, need routine.'
Children need routine.