Sentence Structure Types

Why This Matters

On the PSAT, you're not just being tested on whether you can spot a grammatical error—you're being tested on whether you understand how sentences work. The Writing and Language section frequently asks you to combine sentences, fix run-ons, or choose the most effective revision. If you can't identify whether you're dealing with an independent clause, a dependent clause, or a fragment, you'll struggle to answer these questions confidently.

Sentence structure also matters for the Reading section. Complex and compound-complex sentences can trip you up if you don't know how to parse them quickly. Understanding subordination, coordination, and sentence purpose helps you cut through dense passages and identify main ideas faster. Don't just memorize definitions here—know what each structure does and when writers choose one over another.

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Structures Based on Clause Combinations

These four types are defined by how many independent and dependent clauses they contain. Independent clauses express complete thoughts; dependent clauses cannot stand alone.

Simple Sentences

• One independent clause only—contains a subject and verb expressing a complete thought
• No dependent clauses—the sentence may have compound subjects or verbs, but only one main clause
• PSAT trap: Don't confuse a simple sentence with a long subject or multiple modifiers for a compound sentence

Compound Sentences

• Two or more independent clauses—joined by a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so)
• Comma placement is key—place a comma before the conjunction when joining two independent clauses
• Common error: Using a comma alone creates a comma splice; the PSAT tests this constantly

Complex Sentences

• One independent clause + one or more dependent clauses—the dependent clause adds information but can't stand alone
• Subordinating conjunctions signal dependence—words like although, because, when, if, while introduce dependent clauses
• Comma rule: When the dependent clause comes first, use a comma after it; when it comes second, usually no comma needed

Compound-Complex Sentences

• At least two independent clauses + at least one dependent clause—the most layered structure
• Tests reading comprehension—these sentences require you to identify the main ideas buried within multiple clauses
• Writing flexibility: Allows for nuanced expression of cause-effect, contrast, and sequence in a single sentence

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Structures Based on Purpose

These types are defined by what the sentence is trying to accomplish—stating, asking, commanding, or exclaiming.

Declarative Sentences

• Makes a statement or expresses information—the most common sentence type in academic writing
• Ends with a period—straightforward and factual in tone
• PSAT context: Most passage sentences are declarative; recognize when a shift to another type signals emphasis or tone change

Interrogative Sentences

• Asks a question—begins with a question word (who, what, where, when, why, how) or an auxiliary verb
• Ends with a question mark—signals that a response or consideration is expected
• Rhetorical use: Authors use interrogative sentences to engage readers or introduce ideas they'll answer

Imperative Sentences

• Gives a command or instruction—the subject you is usually implied, not stated
• Can end with a period or exclamation mark—depends on the urgency of the command
• Tone indicator: Imperative sentences in passages often signal a persuasive or instructional purpose

Exclamatory Sentences

• Expresses strong emotion—surprise, excitement, anger, or emphasis
• Ends with an exclamation mark—use sparingly in formal writing
• PSAT relevance: Rare in academic passages, so their presence signals heightened emotion or informal tone

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Structures Based on Information Flow

These types are defined by where the main idea appears—at the beginning or the end.

Loose Sentences (Cumulative)

• Main idea comes first—followed by additional details, modifiers, or explanations
• Creates a conversational, flowing tone—easy to follow because the core meaning arrives early
• Example structure: "She won the race, crossing the finish line with arms raised, tears streaming down her face."

Periodic Sentences

• Main idea is delayed until the end—builds suspense or emphasis through the sentence
• Creates a formal, dramatic effect—forces the reader to hold multiple ideas before reaching the point
• PSAT application: Periodic sentences often appear in rhetoric-focused questions about author's style or emphasis

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Quick Reference Table

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Self-Check Questions

1. What distinguishes a compound sentence from a complex sentence, and which requires a subordinating conjunction?

2. You need to combine two sentences to show that one event caused another. Would you create a compound or complex sentence, and what conjunction might you use?

3. Which two sentence types can both end with exclamation marks, and how do their purposes differ?

4. A passage contains a sentence that delays its main point until the final clause. What type of sentence is this, and what effect does this structure create?

5. Compare loose and periodic sentences: if an author wants to create suspense before revealing a key idea, which structure should they choose, and why?