Sentence Boundaries (Run-ons, Fragments) — SAT Reading & Writing Explained
A complete sentence requires a subject and a predicate and expresses a complete thought. Run-on sentences improperly join two independent clauses; sentence fragments are missing a subject, verb, or complete thought.
The Core Idea
Every sentence must be able to stand alone as a complete thought. Recognizing when a sentence is incomplete (fragment) or when two sentences have been improperly merged (run-on) is the foundation of correct sentence structure.
Types Of Run Ons
Two independent clauses joined only by a comma: 'I studied, I passed.'
Two independent clauses with no punctuation: 'I studied I passed.'
Correction Methods
Create two separate sentences.
Use a semicolon when the ideas are closely related.
Add a comma + FANBOYS (for, and, nor, but, or, yet, so).
Make one clause dependent: 'Because I studied, I passed.'
Fragment Types
'Ran down the street.' → Who ran?
'The tall woman in the red coat.' → What did she do?
'Although she studied.' → Incomplete thought.
Common Errors to Avoid
Thinking a long sentence cannot be a fragment
Using a comma where a period or semicolon is required
Not recognizing that 'although,' 'because,' 'when' make a clause dependent
How This Connects to Other Topics
Works with Comma Usage and Semicolons and Colons for punctuation-based corrections
Practice: Sentence Boundaries (Run-ons, Fragments)
5 SAT-style questions. Select your answer and get an instant explanation.
She missed the train she forgot her umbrella.
Which revision corrects the sentence?
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