SAT Grammar Rules

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Why This Matters

The SAT Writing and Language section isn't testing whether you "sound right"—it's testing whether you can identify and apply specific grammatical principles. Every question on this section connects to a finite set of rules: agreement, punctuation, sentence structure, and clarity. The students who score highest aren't necessarily the best writers; they're the ones who recognize which rule is being tested and apply it systematically.

Here's the key insight: the SAT uses the same patterns repeatedly. Once you understand why a comma belongs in a certain spot or how parallel structure works, you'll spot these patterns instantly. Don't just memorize "use a semicolon between independent clauses"—understand that the SAT is testing whether you know what makes a clause independent in the first place. Master the underlying logic, and you'll handle any variation they throw at you.

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Agreement Rules

These rules ensure that related parts of a sentence match in number, person, or form. The SAT loves to test agreement by inserting distracting phrases between subjects and verbs or pronouns and antecedents.

Subject-Verb Agreement

• Singular subjects take singular verbs; plural subjects take plural verbs—ignore prepositional phrases between them (the box of chocolates was not were)
• Indefinite pronouns like everyone, each, nobody, and anyone are always singular and require singular verbs
• Compound subjects joined by "or" or "nor" match the verb to the nearest subject (Neither the students nor the teacher was ready)

Pronoun Agreement and Clarity

• Pronouns must match their antecedents in number—a singular noun requires it, not they (though SAT now accepts singular they for gender-neutral reference)
• Ambiguous antecedents are automatic wrong answers—if a pronoun could refer to multiple nouns, the sentence needs revision
• Collective nouns like team or committee take singular pronouns when acting as one unit (The team celebrated its victory)

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Sentence Structure

These rules govern how clauses and phrases connect. The SAT tests whether you can distinguish independent clauses from dependent ones and join them correctly.

Sentence Fragments and Run-Ons

• Fragments lack a subject, verb, or complete thought—dependent clauses standing alone (Because she studied hard) are fragments, not sentences
• Run-on sentences improperly fuse two independent clauses—fix them with a period, semicolon, or comma + coordinating conjunction
• Comma splices join independent clauses with only a comma—the SAT treats these as incorrect every time

Coordinating and Subordinating Conjunctions

• FANBOYS (for, and, nor, but, or, yet, so) connect equal grammatical elements and require a comma before them when joining independent clauses
• Subordinating conjunctions (although, because, since, while) create dependent clauses that cannot stand alone
• Placement matters—a subordinating conjunction at the start of a sentence requires a comma after the dependent clause; mid-sentence typically needs no comma

Parallel Structure

• Items in a list must share the same grammatical form—all nouns, all gerunds, or all infinitives (She likes running, swimming, and biking not to bike)
• Comparisons require parallelism—what comes after than or as must mirror what comes before
• Paired constructions (not only...but also, either...or, both...and) demand matching structures on each side

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Punctuation Rules

Punctuation questions test whether you understand the grammatical relationships between sentence parts. Every punctuation mark has specific rules—the SAT doesn't accept "it sounds right."

Comma Usage

• Use commas after introductory elements—phrases or clauses that come before the main subject and verb need a comma (After the storm, the town rebuilt)
• FANBOYS rule: place a comma before coordinating conjunctions joining two independent clauses, but not when joining two verbs or phrases
• Non-essential information gets commas on both sides—if you can remove it without breaking the sentence, it needs commas

Semicolon and Colon Usage

• Semicolons connect two independent clauses without a conjunction—both sides must be complete sentences (She studied hard; she passed the exam)
• Colons introduce explanations, lists, or elaborations but only after an independent clause—what comes before the colon must stand alone
• Semicolons in complex lists separate items that already contain commas (We visited Paris, France; London, England; and Rome, Italy)

Apostrophe Usage

• Possessive nouns use apostrophes (the student's book for singular, the students' books for plural)
• It's vs. its is heavily tested—it's always means it is or it has; its shows possession (The dog wagged its tail)
• Plural nouns never use apostrophes unless showing possession—the 1990s not the 1990's

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Modifier Rules

Modifiers describe or limit other words. The SAT tests whether modifiers are placed correctly and whether the thing being modified is actually present in the sentence.

Modifier Placement

• Modifiers must sit next to what they modify—Running down the street, the dog chased the boy means the dog was running, not the boy
• Dangling modifiers occur when the intended subject is missing—Walking into the room, the lights were off is wrong because lights can't walk
• Misplaced modifiers create unintended meanings—She almost drove her kids to school every day vs. She drove her kids to school almost every day

Logical Comparison

• Compare like to like—The population of Texas is larger than California is wrong; it should be larger than that of California or larger than California's
• Use "than" for comparisons and "as...as" for equivalence—don't mix them up
• Comparative vs. superlative: use -er/more for two items, -est/most for three or more (taller for two people, tallest for a group)

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Word Choice and Style

These rules test precision and clarity. The SAT wants the most concise option that maintains meaning—extra words are almost always wrong.

Redundancy and Concision

• Eliminate redundant phrases—past history, future plans, completely eliminate all contain unnecessary repetition
• Choose the shortest answer that preserves meaning—if two options say the same thing, pick the shorter one
• Avoid wordy constructions—the reason why is because should be because; in order to should be to

Diction and Word Choice

• Commonly confused words are heavily tested—affect/effect, accept/except, then/than, who/whom
• Tone consistency matters—don't mix formal and informal language within a passage
• Precise vocabulary beats vague language—walked slowly is weaker than ambled or trudged

Idioms and Prepositions

• Idiomatic expressions must use correct prepositions—different from (not than), capable of (not to), interested in (not about)
• Preposition + gerund combinations follow patterns—succeeded in achieving, prevented from going
• No logical rule exists—you either know the idiom or you don't, so exposure through reading is key

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Quick Reference Table

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Self-Check Questions

1. Both subject-verb agreement and pronoun-antecedent agreement test matching—what's the key difference in how the SAT typically disguises errors in each?

2. You see a sentence with two complete thoughts joined by a comma. What are three ways to fix this comma splice, and which punctuation mark requires no conjunction?

3. Compare dangling modifiers and misplaced modifiers: which one requires adding or changing the subject, and which one just needs repositioning?

4. A colon and a semicolon can both follow an independent clause. How do you decide which one to use?

5. If an SAT question gives you four answer choices and two of them express the same meaning but one is shorter, which should you choose and why?