SAT Grammar Rules

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Why This Matters

The SAT Writing and Language section tests whether you can identify and apply specific grammatical principles. Every question connects to a finite set of rules: agreement, punctuation, sentence structure, and clarity. The highest-scoring students aren't necessarily the best writers; they're the ones who recognize which rule is being tested and apply it consistently.

The SAT uses the same patterns over and over. Once you understand why a comma belongs in a certain spot or how parallel structure works, you'll spot these patterns quickly. 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 is correct, not were, because the subject is box, not chocolates.
• Indefinite pronouns like everyone, each, nobody, and anyone are always singular and require singular verbs. Each of the students has a textbook, not have.
• Compound subjects joined by "or" or "nor" match the verb to the nearest subject: Neither the students nor the teacher was ready. If you flip the order, it becomes Neither the teacher nor the students were ready.

Pronoun Agreement and Clarity

• Pronouns must match their antecedents in number. A singular noun requires a singular pronoun. The SAT does accept singular they when referring to a person of unspecified gender.
• Ambiguous antecedents are automatic wrong answers. If a pronoun could refer to more than one noun, the sentence needs revision. For example: When Sarah met Julia, she was nervous. Who was nervous? The SAT will always prefer the version that replaces she with a specific name.
• 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, a verb, or a complete thought. A dependent clause standing alone (Because she studied hard.) is a fragment, not a sentence, even though it has a subject and verb. The word because makes it dependent.
• Run-on sentences improperly fuse two independent clauses with no punctuation at all: She studied hard she passed the exam.
• Comma splices join independent clauses with only a comma: She studied hard, she passed the exam. The SAT treats these as incorrect every time. Fix either error with a period, a semicolon, or a comma + coordinating conjunction.

Coordinating and Subordinating Conjunctions

• FANBOYS (for, and, nor, but, or, yet, so) connect equal grammatical elements. When joining two independent clauses, place a comma before the conjunction. When joining just two verbs or phrases (not full clauses), skip the comma.
• 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: Although she studied, she failed. When the dependent clause comes second, you typically don't need a comma: She failed although she studied.

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 running, swimming, and 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. She not only sings but also dances — not she not only sings but also is a dancer.

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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 a coordinating conjunction joining two independent clauses, but not when joining two verbs or phrases. She studied hard and passed the exam needs no comma because passed the exam isn't an independent clause.
• Non-essential information gets commas on both sides. If you can remove it without breaking the sentence's grammar or core meaning, it needs commas: My brother, who lives in Texas, is visiting. If the information is essential to identifying the noun, no commas: Students who study regularly perform better.

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 as a sentence. She had one goal: passing the exam.
• 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. If you can substitute it is into the sentence and it still makes sense, use it's. Otherwise, use its.
• 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, because dog is the subject right after the comma.
• Dangling modifiers occur when the intended subject is missing from the sentence entirely. Walking into the room, the lights were off is wrong because the lights can't walk. You'd need to rewrite: Walking into the room, she noticed the lights were off.
• Misplaced modifiers create unintended meanings by being in the wrong position. She almost drove her kids to school every day suggests she nearly drove but didn't. She drove her kids to school almost every day is what the writer actually means.

Logical Comparison

• Compare like to like. The population of Texas is larger than California is wrong because it compares a population to a state. 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 when comparing 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, and completely eliminate all contain unnecessary repetition. History is already past. Plans are already future.
• 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. At this point in time should be now.

Diction and Word Choice

• Commonly confused words are heavily tested: affect/effect, accept/except, then/than, who/whom. Affect is usually a verb (to influence); effect is usually a noun (a result). Who is for subjects; whom is for objects.
• Tone consistency matters. Don't mix formal and informal language within a passage. If the passage uses academic language, the correct answer will too.
• Precise vocabulary beats vague language. The SAT prefers specific word choices that convey exact meaning.

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 set patterns: succeeded in achieving, prevented from going.
• No logical rule governs idioms. You either know the correct preposition or you don't, so exposure through reading is the best preparation.

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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?