The SAT‘s Reading & Writing section tests grammar in a specific way. There’s no reciting rules or labeling parts of speech. The test hands you a sentence with one thing wrong and asks you to fix it. Sounds simple. The catch is that the SAT is carefully engineered so that wrong answers feel natural and right answers feel awkward. The students who consistently get these right are the ones who understand why a rule exists, not just what it says.

After 20+ years of SAT tutoring and several editions of Barron’s SAT prep books, the same grammar patterns keep coming up on the test. Below are the categories that matter most and the specific traps the SAT sets in each one.

Study the rules interactively: I’ve put together a free reference covering all 38 essential SAT grammar rules, organized by category. Each rule includes an explanation, a correct example, an incorrect example, and a targeted SAT tip.

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Punctuation: The Most Tested Category

Punctuation questions cover commas, semicolons, colons, dashes, and apostrophes, and they make up a large share of the grammar on the digital SAT. Punctuation follows strict, learnable rules. The catch is that most students picked them up loosely along the way and have a lot of “sounds right” habits to unlearn.

Commas are by far the most tested punctuation mark. The SAT tests nine distinct comma rules: when to use one with a coordinating conjunction (only when joining two independent clauses), when to set off non-essential clauses, and, surprisingly often, when not to use one at all. The trap the test runs most: a comma before “and” when the second half of the sentence isn’t a complete clause. “She studied hard, and passed the exam” is wrong because “passed the exam” has no subject of its own.

Semicolons are simpler than most students think. A semicolon can only connect two independent clauses, meaning two parts that could each stand alone as complete sentences. Replace the semicolon with a period: if both halves still work as sentences, the semicolon’s correct. If one half is a phrase or a dependent clause, the semicolon’s wrong. There isn’t more to the rule than that, which is why our semicolons and sentence boundaries drill is one of the higher-payoff places to spend an hour. If you find the rule clicking, our second semicolons drill is the natural next step.

Colons follow an equally clean rule: whatever comes before the colon has to be a complete sentence on its own. Students frequently write things like “My goals are: to finish early and sleep well.” But “My goals are” isn’t a complete sentence, so the colon’s wrong. The check is to cover everything before the colon and ask whether it could stand alone. If not, drop the colon or restructure. Practice this in our colons and dashes drill, then push yourself with drill 2.

Dashes trip students up because they look like commas but work differently. Two dashes interrupting mid-sentence have to work as a matched pair: whatever opens the interruption with a dash must close it with one too. You can’t open with a dash and close with a comma. A single dash at the end of a clause introduces an elaboration or a surprise, and it functions a lot like a colon in that position.

Apostrophes come down to three things: singular possession (add ‘s, always, even for words ending in s), plural possession (just an apostrophe after the s for regular plurals), and the its/it’s distinction. That last one is among the most frequently tested traps on the entire test. “It’s” always means “it is” or “it has.” “Its” is possessive and never takes an apostrophe. Substitute “it is” wherever you see “it’s.” If the sentence breaks, drop the apostrophe.

Verb Agreement: Harder Than It Looks

Subject-verb agreement seems basic until the SAT starts hiding the subject. The favorite technique: insert a long prepositional phrase between the subject and the verb so students match the verb to the wrong noun. “The list of requirements are long” sounds fine because “requirements” is sitting right next to “are.” But the subject is “list,” which is singular, so the correct verb is “is.” Mentally cross out everything between the subject and the verb and check the agreement in isolation. The verb tense and form drill is built around this kind of question, and drill 2 gives you a second pass on the pattern.

The test also leans on inverted sentences that start with “there” or “here.” In “There is three main reasons for the delay,” the subject isn’t “there.” It’s “reasons,” which is plural. Flip the sentence: “Three main reasons are there.” The agreement issue jumps out.

Collective nouns are another reliable trap. On the SAT, words like team, committee, group, and jury are always treated as singular in American English. “The committee have reached their decision” is wrong; “the committee has reached its decision” is correct.

Pronouns: Two Separate Issues

Pronoun questions involve one of two things: agreement or case. Agreement means the pronoun has to match its antecedent in number. The trap here is that the SAT will use “their” with a singular antecedent, which has become acceptable in everyday speech but is still wrong on the test. “Every student must submit their own work” sounds natural, but the SAT expects strict number consistency. Our pronoun-antecedent agreement drill drills exactly this pattern, and drill 2 is good for reinforcement.

Case means using the right pronoun form for the role the pronoun plays in the sentence. Object pronouns (me, him, her, us, them) come after prepositions. “Between you and I” is one of the most common errors in English, and the SAT tests it regularly. Remove the other person and you’d never say “between I.” The preposition needs an object pronoun, so “between you and me” is correct.

Pronoun shift, switching from “one” or “a person” to “you” partway through a sentence, comes up often too. A sentence that opens “When one works hard” has to stay in third person: “one tends to succeed,” not “you tend to succeed.”

Modifier Placement: Logic Over Grammar

Modifier questions test whether a descriptive phrase is logically connected to the right noun. An introductory participial phrase has to modify the grammatical subject of the main clause, which is the first noun after the comma. “Running through the park, a deer was spotted” is wrong because the deer isn’t doing the running. The correct version puts a logical subject in place: “Running through the park, she spotted a deer.” Drill this pattern directly in our modifier placement drill, then check your progress with drill 2.

The that/which distinction is closely related and gets tested often. “That” introduces essential (restrictive) clauses, the kind of information needed to pin down which noun you mean. “Which” introduces non-essential clauses, which add extra information and are set off by commas. “The book that won the award” specifies which book. “The book, which won the award,” adds information about a book that’s already been identified. If you can remove the clause without losing the sentence’s core meaning, use “which” with commas.

Transitions: Matching the Logic Between Ideas

Transition questions ask you to pick the word that correctly signals the logical relationship between two ideas. The test usually gives you four options (a contrast word, an addition word, a cause-and-effect word, and an illustration word), and your job is to read both clauses carefully and figure out which relationship is actually there. Our transitions and connectors drill works through real examples of each relationship type, and drill 2 mixes the relationships in less predictable ways.

The most common trap is picking the word that sounds sophisticated instead of the one that fits. Students reach for “however” when the sentence actually calls for “furthermore,” or use “consequently” when the second clause is an example rather than a result. Read the two ideas first. Figure out whether they agree or disagree, whether one causes the other, or whether the second illustrates the first. Then match the transition to that relationship.

Verb Tense: Consistency and Sequence

Tense questions come in two forms. The first is simple consistency: if a passage is written in the past tense, a verb that randomly shifts to present is wrong. Always scan the surrounding sentences for tense context before choosing. The underlined portion isn’t isolated from what’s around it.

The second form involves sequence of events. The past perfect (had + past participle) shows that one past action was completed before another. Signal words like “by the time,” “before,” and “after” are the SAT’s way of telling you that sequencing matters in that sentence. “By the time she arrived, the meeting ended” should be “the meeting had ended,” since it was done before she got there. Verb tense drill 3 has more sequencing questions like this if it’s a pattern you want to work on.

Conditionals are tested too. Real or possible conditions use present + future: “If she studies, she will pass.” Hypothetical conditions use past + would: “If she studied, she would pass.” The trap the SAT runs almost every time involves “would” in the if-clause. Never write “If she would study.” “Would” belongs in the result clause, not the condition.

What to Practice Next

The seven categories above (commas, other punctuation, verb agreement, pronouns, modifier placement, verb tense, and transitions) cover the vast majority of grammar questions on the digital SAT. The work isn’t memorizing rules in the abstract. It’s recognizing the specific traps the test sets in each category and building habits for catching them.

Once you’ve reviewed the rules, put them to work in context with our SAT Reading & Writing practice drills, a set of 40 drills covering every question type, each with five questions and full explanations. If you want to build the vocabulary that pays off on the harder Reading & Writing questions, the SAT Vocabulary Flashcards are a natural complement to grammar work. And for math alongside your Reading & Writing prep, the SAT Math drills are organized the same way, by skill and question type.

Free SAT Grammar Rules Reference — all 38 rules across 7 categories, with explanations, correct and incorrect examples, and targeted SAT tips for each one. Browse the full list or expand individual sections as you study.

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