Reading and Writing · 17 · Sentence Rules
Sentences, Phrases and Clauses
Notes
Key points
- Clause = subject + verb. Phrase = missing one of them.
- Independent clause: can stand alone as a sentence.
- Dependent clause: starts with because, although, when, which, that… — can't stand alone.
- A sentence needs at least one independent clause. Less = fragment.
- Two independent clauses + comma only = comma splice. Nothing between = run-on.
- Length proves nothing: a long string of words can still be a fragment.
Rules
A dependent clause needs an independent clause attached.
Because the road was closed, we took the train.
Because the road was closed. We took the train.
A sentence needs a subject and a finite verb.
The museum, which opened in 1902, houses rare maps.
The museum, which opened in 1902, housing rare maps.
A relative clause alone is a fragment.
She met the author, who signed her copy.
She met the author. Who signed her copy.
Common traps
- Missing that the main verb vanished after a long “which” clause.
- Choosing a period that strands a dependent clause as its own sentence.
SAT tip
Boundary question? Split the text at the blank and label each side: independent or dependent. Then pick the punctuation.
Test yourself
10 official SAT questions on Sentences, Phrases and Clauses, easiest first.