What is Sentence Structure?

Identify and correct sentence structure errors including fragments, run-ons, comma splices, misplaced modifiers, and faulty parallelism.

How can I study Sentence Structure effectively?

Start by reading the study notes and working through the examples on this page. Then use the flashcards to test your recall. Practice with the 13 problems provided, checking solutions as you go. Regular review and active practice are key to retention.

Is this Sentence Structure study guide free?

Yes — all study notes, flashcards, and practice problems for Sentence Structure on Study Mondo are 100% free. No account is needed to access the content.

What course covers Sentence Structure?

Sentence Structure is part of the SAT Prep course on Study Mondo, specifically in the SAT Reading and Writing section. You can explore the full course for more related topics and practice resources.

Are there practice problems for Sentence Structure?

Yes, this page includes 13 practice problems with detailed solutions. Each problem includes a step-by-step explanation to help you understand the approach.

Sentence Structure

Sentence Types

Simple: One independent clause. "The dog barked."
Compound: Two independent clauses joined by conjunction or semicolon. "The dog barked, and the cat hissed."
Complex: One independent + one dependent clause. "When the dog barked, the cat hissed."
Compound-Complex: Multiple independent + at least one dependent clause.

Fragments (Always Wrong on the SAT)

A fragment is a group of words that looks like a sentence but lacks a subject, a verb, or a complete thought.

"Running through the park on a sunny day." (no subject + finite verb)
"Because the experiment was successful." (dependent clause alone)

Run-On Sentences (Always Wrong)

A run-on joins two independent clauses without proper punctuation or conjunction.

Fused sentence: "I ran she walked"
Comma splice: "I ran, she walked"

Fixes for Run-Ons

Period: "I ran. She walked."

❓ Question:

Which is correct?

A) I love reading, my sister prefers sports. B) I love reading; my sister prefers sports. C) I love reading my sister prefers sports.

Solution:

Two complete sentences:

"I love reading"
"My sister prefers sports"

Check each option:

A) Comma alone (comma splice) ❌ B) Semicolon (correct way to join) ✓ C) No punctuation (run-on) ❌

❓ Question:

Which is correct?

A) Walking to school, the rain started falling. B) Walking to school, I felt the rain start falling. C) Walking to school, it rained. D) The rain, walking to school, started.

Solution:

Opening modifier: "Walking to school"

Rule: Must describe the subject immediately after comma

Check each:

A) The rain walked to school? ❌ B) "I" walked to school ✓ (makes sense!) C) "It" (rain) walked to school? ❌ D) Awkward/unclear ❌

Answer: B

SAT Tip: Opening modifying phrase must clearly describe the subject that follows!

❓ Question:

Which maintains parallel structure?

A) The goals are to increase revenue, reducing costs, and improve efficiency. B) The goals are to increase revenue, to reduce costs, and improving efficiency. C) The goals are to increase revenue, to reduce costs, and to improve efficiency. D) The goals are increasing revenue, to reduce costs, and to improve efficiency.

Solution:

Parallel structure: All items must have same form

Check each:

A) to increase, reducing, improve (THREE DIFFERENT FORMS) ❌ B) to increase, to reduce, improving (NOT ALL SAME) ❌ C) to increase, to reduce, to improve (ALL INFINITIVES) ✓ D) increasing, to reduce, to improve (NOT ALL SAME) ❌

Answer: C

SAT Tip: In a list, all items should match: all infinitives, all -ing forms, all nouns, etc.

❓ Question:

Identify the error: "Running through the park on a sunny afternoon."

Error: This is a sentence fragment — it has no main subject and verb.

"Running through the park on a sunny afternoon" is a participial phrase. It describes an action but doesn't tell us WHO is doing it and doesn't have a complete predicate.

Fix options:

Add a subject and verb: "She was running through the park on a sunny afternoon." ✅
Attach to a complete sentence: "Running through the park on a sunny afternoon, she felt free." ✅

What makes a complete sentence:

A subject (who/what)
A verb (action/state)
A complete thought

Answer: Fragment — needs a subject and a main verb to be complete.

❓ Question:

Identify the error: "Running through the park on a sunny afternoon."

Error: This is a sentence fragment — it has no main subject and verb.

"Running through the park on a sunny afternoon" is a participial phrase. It describes an action but doesn't tell us WHO is doing it and doesn't have a complete predicate.

Fix options:

Add a subject and verb: "She was running through the park on a sunny afternoon." ✅
Attach to a complete sentence: "Running through the park on a sunny afternoon, she felt free." ✅

What makes a complete sentence:

A subject (who/what)
A verb (action/state)
A complete thought

Answer: Fragment — needs a subject and a main verb to be complete.

❓ Question:

Combine these sentences effectively: "The experiment yielded surprising results. The scientists decided to repeat it. They wanted to confirm their findings."

Option 1 — Subordination: "Because the experiment yielded surprising results, the scientists decided to repeat it to confirm their findings." ✅ (Uses "because" to show cause-effect; "to confirm" combines sentences 2 and 3)

Option 2 — Relative clause: "The experiment, which yielded surprising results, prompted the scientists to repeat it to confirm their findings." ✅

Option 3 — Participial phrase: "Surprised by the results, the scientists decided to repeat the experiment to confirm their findings." ✅

Avoid:

"The experiment yielded surprising results, and the scientists decided to repeat it, and they wanted to confirm their findings." ❌ (Too many "ands" — choppy)

SAT Principle: The most concise, clear combination is usually the best answer. Avoid unnecessary words and repetition.

Answer: "Because the experiment yielded surprising results, the scientists decided to repeat it to confirm their findings."

❓ Question:

Combine these sentences effectively: "The experiment yielded surprising results. The scientists decided to repeat it. They wanted to confirm their findings."

Option 2 — Relative clause: "The experiment, which yielded surprising results, prompted the scientists to repeat it to confirm their findings." ✅

Option 3 — Participial phrase: "Surprised by the results, the scientists decided to repeat the experiment to confirm their findings." ✅

Avoid:

"The experiment yielded surprising results, and the scientists decided to repeat it, and they wanted to confirm their findings." ❌ (Too many "ands" — choppy)

SAT Principle: The most concise, clear combination is usually the best answer. Avoid unnecessary words and repetition.

Answer: "Because the experiment yielded surprising results, the scientists decided to repeat it to confirm their findings."

❓ Question:

Fix the run-on sentence: "The storm knocked out power to the entire neighborhood residents had to use candles and flashlights for three days."

This is a run-on sentence — two independent clauses with no punctuation or conjunction between them.

Fix 1 — Period: "The storm knocked out power to the entire neighborhood. Residents had to use candles and flashlights for three days."

Fix 2 — Semicolon: "The storm knocked out power to the entire neighborhood; residents had to use candles and flashlights for three days."

Fix 3 — Comma + conjunction: "The storm knocked out power to the entire neighborhood, so residents had to use candles and flashlights for three days."

Fix 4 — Subordination: "After the storm knocked out power to the entire neighborhood, residents had to use candles and flashlights for three days."

Best for SAT: Fix 4 (subordination) is often the best answer because it shows the relationship between the clauses (cause → effect).

Answer: Any of these fixes would work; subordination shows the clearest logical connection.