TOEFL Grammar: Academic cohesion and punctuation 10 hard-level rules, each shown with a correct sentence, the mistake learners most often make instead, and the TOEFL tasks where it counts.
Test Ninjas Research · Updated October 1, 2026
However, therefore, semicolons, colons and paired commas: the tools that connect sentences and show how ideas relate. They carry a discussion post from one point to the next, and their punctuation rules are strict enough to be worth learning precisely.
Part of the
TOEFL grammar guide : 120 rules in 12 topics. The cards are original teaching material checked against the linked references; they are not an ETS syllabus.
The rules 1. However between clauses Place a period or semicolon before however when it connects two independent clauses.
Correct The sample was small; however, the trend was clear.
Common trap · incorrect The sample was small, however, the trend was clear.
What goes wrong: the trap gets the punctuation wrong, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Commas vs. Semicolons in Compound Sentences
2. Therefore between clauses Do not use therefore alone as the grammatical join between two complete clauses.
Correct The lab was full. Therefore, we met online.
Common trap · incorrect The lab was full therefore we met online.
What goes wrong: the trap gets the punctuation wrong, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Commas vs. Semicolons in Compound Sentences
3. Semicolon and complete clauses A semicolon joining clauses needs a complete clause on each side.
Correct The survey closed; the results were posted.
Common trap · incorrect The survey closed; because the results were posted.
What goes wrong: the trap adds “because”, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Commas vs. Semicolons in Compound Sentences
4. Colon after a complete clause Put a colon after a complete clause when it introduces an explanation or example.
Correct One issue remained: the sample was too small.
Common trap · incorrect One issue was: the sample was too small.
What goes wrong: the trap uses “was” where the correct sentence has “remained”, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Punctuation Vidcast Transcript
5. Paired commas in an aside A nonessential clause in the middle of a sentence needs a closing comma as well as an opening one.
Correct The library, which was renovated last year, is open.
Common trap · incorrect The library, which was renovated last year is open.
What goes wrong: the trap gets the punctuation wrong, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Commas with Nonessential Elements
6. For example as a transition In formal prose, set off for example when it starts a new illustrative sentence.
Correct Several tools can help. For example, a checklist can prevent omissions.
Common trap · incorrect Several tools can help for example a checklist can prevent omissions.
What goes wrong: the trap gets the punctuation wrong, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Sources: For example ; Commas After Introductions
7. Such as before examples Use such as before a noun phrase giving examples of a larger category.
Correct Methods such as interviews can reveal preferences.
Common trap · incorrect Methods such as to interview can reveal preferences.
What goes wrong: the trap uses “to interview” where the correct sentence has “interviews”, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Such as
8. Whereas with clauses Join two complete contrasting clauses with whereas.
Correct The first method is faster, whereas the second is cheaper.
Common trap · incorrect The first method is faster, whereas the second to be cheaper.
What goes wrong: the trap uses “to be” where the correct sentence has “is”, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Whereas
9. This plus a summary noun After a complex claim, a noun after this can make the reference precise.
Correct The lab closed, so the exam moved online. This change of format confused students.
Common trap · incorrect The lab closed, so the exam moved online. This confused students.
What goes wrong: the trap leaves out “change of format”, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Sentence Clarity
10. In addition to plus ing After in addition to, use a noun phrase or an ing phrase rather than a finite clause.
Correct In addition to revising the chart, she checked the numbers.
Common trap · incorrect In addition to she revised the chart, she checked the numbers.
What goes wrong: the trap uses “she revised” where the correct sentence has “revising”, so it no longer follows the rule.
Matters for: Write an Email · Academic Discussion
Source: Conjunctions: adding
Previous ← Conditionals and modality Next Agreement and parallelism → Other grammar topics
Frequently Asked Questions Which TOEFL tasks test academic cohesion and punctuation? + No task names grammar topics, but these rules matter most in Write an Email, Academic Discussion. Build a Sentence rewards correct word order and forms directly; in emails, discussion posts and spoken answers, errors here make your meaning harder to follow.
Are these official TOEFL grammar rules? + No. ETS does not publish a grammar syllabus. These are original Test Ninjas teaching cards based on standard English usage, with links to the reference pages each rule was checked against.
How should I practice these rules? + Read the rule, then cover the correct sentence and try to fix the trap yourself. Next, write one new sentence of your own that follows the rule, ideally about a campus or class situation.