15 Key SAT Grammar Rules to Remember before the Exam 

Most students lose SAT grammar points not because they don't know the rules. They lose them because they trust how a sentence sounds instead of applying the rule they already know.

The digital SAT builds traps around that instinct. A sentence can read naturally and still be wrong by the test's standards. The Standard English Conventions section includes 14 questions, and every single one maps to one of these 15 rules. Learn them, apply them by identification, and you stop guessing.

Rule 1: Commas

Commas have four uses on the SAT: after an introductory phrase, around non-essential information, between items in a list of three or more, and before a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so) that joins two complete sentences. A comma between a subject and its verb is always wrong.

Incorrect: After the experiment, the team reviewed the data.
Correct: After the experiment, the team reviewed the data.

Practice question: Which option is correct?

She submitted her application early but the deadline was extended anyway.

A) She submitted her application early, but the deadline was extended anyway.
B) She submitted her application early but, the deadline was extended anyway.
C) She submitted her application, early but the deadline was extended anyway.
D) No change needed.

Answer: A. "But" joins two independent clauses. A comma belongs before it.

Rule 2: Semicolons

On the digital SAT, a semicolon and a period are functionally identical. Both join two complete, independent sentences. If an answer choice offers a semicolon and another offers a period in the exact same position, you can eliminate both. If one side of the semicolon cannot stand alone as a sentence, the semicolon is wrong.

Incorrect: The experiment produced unexpected results; changing the team's hypothesis. Correct: The experiment produced unexpected results; the team revised its hypothesis.

Practice question: Which option correctly punctuates the sentence?

The novel won numerous awards _____ it was praised for its vivid characters.

A) The novel won numerous awards, it was praised for its vivid characters.
B) The novel won numerous awards; it was praised for its vivid characters.
C) The novel won numerous awards it was praised for its vivid characters.
D) The novel won numerous awards, and, it was praised for its vivid characters.

Answer: B. Both sides are complete sentences. A semicolon correctly joins them.

Rule 3: Colons and Dashes

Colons and dashes are interchangeable on the SAT. Both introduce a list, explanation, or elaboration. The rule: whatever comes before the colon or dash must be a complete sentence. You cannot place a colon between a verb and its object.

Incorrect: The guide covers: grammar, punctuation, and style.
Correct: The guide covers three topics: grammar, punctuation, and style.

Practice question: Which version uses a colon correctly?

A) The museum displayed: paintings, sculptures, and photographs.
B) The museum displayed three types of art: paintings, sculptures, and photographs.
C) Paintings, sculptures, and photographs: filled the museum's galleries.
D) The museum's: paintings, sculptures, and photographs were displayed.

Answer: B. "The museum displayed three types of art" is a complete sentence. The colon correctly introduces the list.

Rule 4: Comma Splices and Run-On Sentences

A comma splice joins two independent clauses with only a comma. A run-on joins them with no punctuation. The most common SAT trap involves words like "however," "therefore," and "furthermore." Students treat these like coordinating conjunctions. They are not. A comma before "however" between two sentences creates a comma splice every time.

Incorrect: The findings were significant, however the study had limitations.
Correct: The findings were significant; however, the study had limitations. 

Practice question: Which version is grammatically correct?

A) The team worked overnight, therefore the project was completed on time.
B) The team worked overnight; therefore, the project was completed on time.
C) The team worked overnight therefore the project was completed on time.
D) The team worked overnight, and therefore, the project was completed on time.

Answer: B. "Therefore" is a conjunctive adverb. A semicolon must come before it when it connects two independent clauses.

Rule 5: Sentence Fragments

A complete sentence needs a subject, a verb, and a complete thought. Clauses that begin with "although," "because," "since," "while," or "which" cannot stand alone. They need a main clause to be complete. The SAT creates fragments that look and sound like sentences because the missing piece is easy to overlook.

Incorrect: Although the researcher collected years of data. Correct: Although the researcher collected years of data, the results were unclear.

Practice question: Which option is a complete sentence?

A) Because the researchers had not accounted for external variables.
B) The researchers, having not accounted for external variables.
C) While the researchers overlooked several key variables in the study.
D) The researchers had not accounted for several key variables.

Answer: D. It has a subject, a verb, and a complete thought. The other three are dependent clauses or phrases without a main verb.

Rule 6: Subject-Verb Agreement

Singular subjects take singular verbs, and plural subjects take plural verbs. The SAT hides the subject behind a long prepositional phrase to make you forget which noun is actually in charge. Strip out any phrase starting with "of," "in," "with," or "by," find the real subject, then choose the verb.

Incorrect: The quality of the research findings were impressive.
Correct: The quality of the research findings was impressive.

Practice question: Which verb form is correct?

The success of the new environmental policies _____ been difficult to measure.

A) have
B) has
C) were
D) are

Answer: B. Strip out "of the new environmental policies." The subject is "success," which is singular. Use "has."

Rule 7: Verb Tense Consistency

Verbs in a sentence should stay in a consistent tense unless the writing deliberately describes actions happening at different times. The SAT embeds a single rogue tense shift and asks you to correct it. Always look at the surrounding sentences for time-marker words and neighboring verb tenses before choosing.

Incorrect: Last year, the team developed a new method and presents it at the conference. Correct: Last year, the team developed a new method and presented it at the conference.

Practice question: Which sentence has a tense error?

A) The author argues that modern cities often neglect green spaces.
B) The report analyzes recent data and drew conclusions about urban growth.
C) Scientists continue to study the effects of microplastics on marine life.
D) The policy has been revised several times since its initial introduction.

Answer: B. "Analyzes" is present tense; "drew" is past tense. It should be "draws."

Rule 8: Pronoun-Antecedent Agreement

A pronoun must match its antecedent in number. Singular nouns get singular pronouns. The SAT's trap is indefinite pronouns: "everyone," "each," "neither," and "anyone" are always singular, even when they feel plural. Collective nouns like "company," "committee," and "team" take singular pronouns because they act as a single unit.

Incorrect: The company announced that they would be restructuring. Correct: The company announced that it would be restructuring.

Practice question: Which option correctly uses a pronoun?

The organization revised _____ mission statement after the annual review.

A) their
B) its
C) it's
D) they're

Answer: B. "Organization" is singular. "Its" (possessive pronoun, no apostrophe) is correct.

Rule 9: Pronoun Case

Subject pronouns (I, he, she, they, who) perform actions. Object pronouns (me, him, her, them, whom) receive them. The SAT tests this most often with "who" vs. "whom" and compound phrases like "between you and I." Use the substitution trick for who/whom: if "he" fits, use "who"; if "him" fits, use "whom."

Incorrect: Between you and I, the results were surprising.
Correct: Between you and me, the results were surprising.

Practice question: Which pronoun is correct?

_____ did the committee select to lead the project?

A) Who
B) Whom
C) Whoever
D) Whomever

Answer: B. "The committee selected him." "Him" fits, so "whom" is correct.

Rule 10: Apostrophes

Apostrophes show possession or form contractions. They never make a word plural. Possessive pronouns (its, their, whose) never take apostrophes. Test "its" vs. "it's" by substituting "it is." If the substitution makes sense, use "it's." If it does not, use "its."

Incorrect: The company released it's annual report.
Correct: The company released its annual report.

Practice question: Which sentence uses apostrophes correctly?

A) The team's equipment was stored in it's usual location.
B) The teams equipment was stored in its usual location.
C) The team's equipment was stored in its usual location.
D) The teams' equipment was stored in it's usual location.

Answer: C. "Team's" (possessive, one team) and "its" (possessive pronoun, no apostrophe) are both correct.

Rule 11: Modifiers and Modifier Placement

A modifier must sit directly next to the word it describes. When a sentence opens with a descriptive phrase, the noun immediately after the comma must be the thing performing that action. If it cannot logically do so, the modifier is dangling.

Incorrect: After reviewing the data, several patterns became apparent. Correct: After reviewing the data, the researchers identified several patterns.

Practice question: Which option correctly fixes the dangling modifier?

Running through the park, the rain began to fall.

A) Running through the park, the rain began to fall.
B) Running through the park, she was caught in the rain.
C) The rain began to fall as it was running through the park.
D) She ran through the park, rain falling around her and beginning to fall.

Answer: B. The person is running, not the rain. The noun after the comma must be the person.

Rule 12: Parallel Structure

Items in a list or paired construction must share the same grammatical form. If the first item is an infinitive (to run), all items must be infinitives. The SAT tests this in lists and in paired constructions like "not only...but also," "either...or," and "both...and."

Incorrect: The program teaches students to research, write clearly, and critical thinking. Correct: The program teaches students to research, write clearly, and think critically.

Practice question: Which option maintains parallel structure?

The new policy aims to reduce waste, conserve energy, and _____ water usage.

A) minimizing
B) minimization of
C) minimize
D) that it minimizes

Answer: C. "Reduce" and "conserve" are base infinitives. "Minimize" matches that form.

Rule 13: Transition Words

Transition words signal the logical relationship between ideas: contrast (however, although, despite), addition (furthermore, also), cause and effect (therefore, as a result), and example (for instance, specifically). Read both sentences in full, identify the relationship, then choose the transition that matches it.

Incorrect: The study had a large sample. Furthermore, the results may not apply universally. Correct: The study had a large sample. However, the results may not apply universally.

Practice question: Which transition correctly reflects the relationship?

The proposed plan would create thousands of jobs. _____, it would require significant public funding.

A) Furthermore
B) As a result
C) However
D) Therefore

Answer: C. The second sentence presents a drawback, which is a contrast relationship. "However" is correct.

Rule 14: Correlative Conjunctions

Correlative conjunctions are fixed pairs: either...or, neither...nor, not only...but also, both...and, between...and. Both halves must appear, and the items they connect must be grammatically parallel. The most common SAT trap is using "or" after "neither" instead of "nor."

Incorrect: Neither the results or the process was questioned.
Correct: Neither the results nor the process was questioned.

Practice question: Which sentence uses correlative conjunctions correctly?

A) Neither the professor or the students were satisfied with the outcome.
B) The study was both thorough but inconclusive.
C) Either the team will present on Friday, or they will submit a written report.
D) Not only did the experiment fail, or it also wasted resources.

Answer: C. "Either...or" is a correct and complete pair. A uses "or" after "neither" (should be "nor"), B pairs "both" with "but" (should be "and"), and D pairs "not only" with "or" instead of "but also."

Rule 15: Conciseness and Redundancy

The SAT rewards the most concise, clear answer. When two choices are both grammatically correct, the shorter one is almost always right. Redundancy means saying the same thing twice in different words. If removing a word does not change the meaning, the word is redundant and should be cut.

Common redundant phrases: "end result," "past history," "new innovation," "return back," "merge together."

Incorrect: The committee returned back to the original proposal.
Correct: The committee returned to the original proposal.

Practice question: Which option is most concise?

The biography, which is a book about the life of a famous scientist, was published in 2020.

A) The biography, which is a book about the life of a famous scientist, was published in 2020.
B) The biography about the famous scientist was published in 2020.
C) The biographical book that describes the entire life of a well-known scientist was published in 2020.
D) The biography, being a book about a scientist's life, was published in 2020.

Answer: B. "Biography" already means a book about someone's life. The relative clause in A is redundant. B says the same thing with fewer words.

Put the rules to work

Every Standard English Conventions question on the digital SAT comes from one of these 15 rules, no exceptions. The students who improve fastest on this section stop asking "does this sound right?" and start asking "which rule is being tested here?"

That shift in approach is what separates a 650 from a 720 on Reading and Writing. If you're still missing grammar questions after studying these rules, the issue is usually one of two things: you are not identifying the rule fast enough under time pressure, or two to three specific rules are producing most of your errors.

A diagnostic session with one of our SAT tutors tells you exactly which rules are costing you points. Alexander, who scored a perfect 1600 on the SAT, works with students on this section regularly, and 92% of NAT students improved by 90 or more SAT points after working with us.

Book your free intro consultation to find out what your Reading and Writing score could look like with the right strategy behind it.

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