SAT Grammar Rules: The Complete Reference
By the Cheetah Prep team
Almost half of the digital SAT Reading and Writing section is grammar, and it tests a small, fixed set of rules. Learn these 36 and the section stops feeling like a guessing game. Search the full list below, or jump to a topic. Every rule comes with a wrong and a right example, because that is how the SAT actually asks them.
36 rules
Two independent clauses need real punctuation
Sentence BoundariesTwo complete sentences cannot be joined by a comma alone. Use a period, a semicolon, or a comma plus a FANBOYS conjunction.
The experiment failed, the team ran it again the next morning.
The experiment failed, so the team ran it again the next morning.
On the SAT: The most tested grammar concept on the section. The SAT offers the same clause split with a comma, a semicolon, a period, and a dash, and only one is punctuated correctly.
A fragment is missing a subject or a verb
Sentence BoundariesEvery sentence needs a subject and a working verb. A phrase or a dependent clause on its own is a fragment.
Because the bridge, built in 1932, still carrying traffic today.
The bridge, built in 1932, still carries traffic today.
On the SAT: Answer choices sometimes strip the main verb or bury it in an -ing form, leaving no complete sentence.
A dependent clause can attach to an independent one
Sentence BoundariesA dependent clause (starting with words like because, although, when, since) joins an independent clause with just a comma, or with no comma if it comes second.
Although the data was clear; the committee wanted a second study.
Although the data was clear, the committee wanted a second study.
On the SAT: The SAT tests whether you can tell a dependent clause from an independent one, since only two independent clauses need heavy punctuation.
Comma before FANBOYS joining two sentences
CommasWhen for, and, nor, but, or, yet, or so joins two complete sentences, put a comma before it.
The river rose overnight and the town issued a warning.
The river rose overnight, and the town issued a warning.
On the SAT: Watch for a comma dropped before the conjunction, or added before a conjunction that only joins two words.
Comma after an introductory element
CommasA word, phrase, or dependent clause that opens a sentence is followed by a comma.
After finishing the final round of edits the author sent the manuscript.
After finishing the final round of edits, the author sent the manuscript.
On the SAT: Frequently tested with long introductory phrases where the comma is missing or misplaced.
Commas around nonessential information
CommasInformation that can be removed without changing the core meaning gets a pair of commas, one before and one after.
The novelist, who won the prize last year released a sequel.
The novelist, who won the prize last year, released a sequel.
On the SAT: The SAT tests whether you use a matched pair, not just one, and whether the element is actually removable.
No comma between a subject and its verb
CommasNever separate a subject from its verb with a single comma, no matter how long the subject is.
The students who studied every night for a month, passed easily.
The students who studied every night for a month passed easily.
On the SAT: A favorite trap: a long subject followed by a stray comma right before the verb.
No comma before an essential clause
CommasA clause the sentence needs to identify its subject (often starting with that) takes no comma.
The bill, that the senate passed, takes effect in June.
The bill that the senate passed takes effect in June.
On the SAT: The SAT contrasts essential and nonessential clauses; adding a comma to an essential one is wrong.
A semicolon joins two independent clauses
Semicolons, Colons, and DashesUse a semicolon between two complete sentences that are closely related. What sits on each side must be able to stand alone.
The results were surprising; especially the drop in the second trial.
The results were surprising; the drop in the second trial stunned everyone.
On the SAT: The SAT checks that both sides are independent. If one side is a fragment, the semicolon is wrong.
A colon follows a complete sentence
Semicolons, Colons, and DashesA colon introduces a list, an explanation, or an example, but only after an independent clause.
The kit includes: a compass, a map, and a whistle.
The kit includes three items: a compass, a map, and a whistle.
On the SAT: The trap is a colon placed mid-sentence, after a verb or preposition, where nothing complete precedes it.
Dashes mark an interruption, in a matched pair
Semicolons, Colons, and DashesA pair of dashes can set off nonessential information, working like a pair of commas. If you open with a dash, close with a dash.
The theory, once dismissed as fringe - now anchors the field.
The theory, once dismissed as fringe, now anchors the field.
On the SAT: The SAT mixes a dash on one end with a comma on the other; the punctuation on both ends must match.
A single dash can replace a colon
Semicolons, Colons, and DashesOne dash can introduce an explanation or a list after a complete sentence, the same way a colon does.
She had one goal, to finish before sunrise.
She had one goal: to finish before sunrise.
On the SAT: Both a colon and a single dash can be correct here, so the SAT tests whether what precedes it is a full sentence.
Its is possessive; it's means it is
Apostrophes and PossessivesIts shows possession and takes no apostrophe. It's is a contraction of it is or it has.
The company raised it's prices after the merger.
The company raised its prices after the merger.
On the SAT: One of the most tested single distinctions in the section.
Singular possessive adds apostrophe-s
Apostrophes and PossessivesTo make a singular noun possessive, add an apostrophe and an s.
The dogs collar was too tight.
The dog's collar was too tight.
On the SAT: The SAT distinguishes a plural noun from a singular possessive that sound identical when read aloud.
Plural possessive puts the apostrophe after the s
Apostrophes and PossessivesTo make a regular plural noun possessive, add an apostrophe after the existing s.
The teacher collected all the student's essays at once.
The teacher collected all the students' essays at once.
On the SAT: Choices differ only in apostrophe placement: dogs, dog's, and dogs'.
Plurals never take an apostrophe
Apostrophes and PossessivesA plain plural, with no possession, has no apostrophe.
The lab ordered three new microscope's.
The lab ordered three new microscopes.
On the SAT: The SAT adds a stray apostrophe to a simple plural to see if you catch it.
The verb matches the subject, not a nearby noun
Subject-Verb AgreementA phrase between the subject and verb does not change the subject. Find the real subject and match it.
The box of old letters were found in the attic.
The box of old letters was found in the attic.
On the SAT: The SAT inserts a prepositional phrase with a noun of the opposite number right before the verb.
Compound subjects joined by and are plural
Subject-Verb AgreementTwo subjects connected by and take a plural verb.
The director and the lead actor was late to rehearsal.
The director and the lead actor were late to rehearsal.
On the SAT: Tested alongside single subjects that look plural because of an intervening phrase.
In an inverted sentence, the subject follows the verb
Subject-Verb AgreementWhen a sentence starts with there is, there are, or a similar structure, the subject comes after the verb. Match it anyway.
There is several reasons for the delay.
There are several reasons for the delay.
On the SAT: There is and there are questions are common; the noun that follows sets the number.
Collective nouns are usually singular
Subject-Verb AgreementA group acting as one unit (team, committee, jury) takes a singular verb.
The committee disagree about the budget.
The committee disagrees about the budget.
On the SAT: The SAT pairs a collective noun with a plural verb to test whether you treat the group as one.
Tense follows the sentence's time markers
Verb Tense and FormMatch the verb to the time words in the sentence. If it says last year, use past tense.
By the time the storm arrives, the crew already secured the boats.
By the time the storm arrives, the crew will have secured the boats.
On the SAT: The SAT gives a clear time clue and offers verbs in several tenses.
Keep tense consistent within a passage
Verb Tense and FormDo not shift between past and present without a reason. Stay in the tense the passage establishes.
The researcher recorded the data and then analyzes it that evening.
The researcher recorded the data and then analyzed it that evening.
On the SAT: A paragraph in the past tense will offer a present-tense verb to break the pattern.
A pronoun agrees with its antecedent in number
PronounsA singular noun takes a singular pronoun; a plural noun takes a plural pronoun.
Each student must bring their own calculator.
Each student must bring a calculator.
On the SAT: The SAT separates the pronoun from its antecedent so the mismatch is easy to miss.
A pronoun must clearly point to one noun
PronounsIf a pronoun could refer to more than one noun, the sentence is ambiguous and must be rewritten.
When the plate hit the counter, it cracked.
When the plate hit the counter, the plate cracked.
On the SAT: The correct answer often replaces a vague it or they with the actual noun.
Who is a subject; whom is an object
PronounsUse who when the pronoun does the action, whom when it receives the action.
The scientist whom discovered the comet won an award.
The scientist who discovered the comet won an award.
On the SAT: A less common but recurring case-form question.
A modifier sits next to what it describes
ModifiersAn opening descriptive phrase must be followed immediately by the noun it modifies.
Walking to school, the rain soaked my backpack.
Walking to school, I felt the rain soak my backpack.
On the SAT: Classic dangling modifier: the phrase describes a noun that never appears where it should.
Place the modifier as close as possible to its target
ModifiersA misplaced modifier changes the meaning by attaching to the wrong word.
She served sandwiches to the children on paper plates.
She served the children sandwiches on paper plates.
On the SAT: The SAT moves a phrase so it appears to describe the wrong noun.
Items in a list share the same form
Parallel StructureEvery item in a series must match in grammatical form, all nouns or all verbs of the same type.
The internship involved writing reports, data entry, and to answer calls.
The internship involved writing reports, entering data, and answering calls.
On the SAT: The SAT breaks the pattern with one item in a different form.
Comparisons must be parallel
Parallel StructureThe two things being compared must be grammatically and logically alike.
The climate of the coast is milder than the mountains.
The climate of the coast is milder than that of the mountains.
On the SAT: The SAT compares mismatched things, like a person to an action or a book to an author.
The transition must match the logic
TransitionsChoose the transition that fits the relationship: contrast, cause, addition, or example.
The budget was approved. However, the project began the next week.
The budget was approved. Accordingly, the project began the next week.
On the SAT: One of the two most common Writing question types. Read both sentences and name the relationship before you look at the choices.
Contrast words signal a change in direction
TransitionsHowever, nevertheless, and on the other hand mark a shift or a contradiction between ideas.
The trail was steep. Therefore, few hikers turned back.
The trail was steep. Nevertheless, few hikers turned back.
On the SAT: The SAT offers a contrast word where the two ideas actually agree, or the reverse.
Cause-and-effect words show a result
TransitionsTherefore, thus, consequently, and as a result signal that the second idea follows from the first.
Ticket sales doubled. In contrast, the venue added a second show.
Ticket sales doubled. Consequently, the venue added a second show.
On the SAT: Tested against contrast and addition transitions that would break the logic.
The SAT rewards the shortest clear option
Concision and StyleWhen every choice is grammatically correct, the most concise one that keeps the meaning is right.
The two twins were both identical to each other in appearance.
The twins were identical.
On the SAT: If four answers all work, pick the shortest. The SAT penalizes wordiness and redundancy.
Cut redundant pairs
Concision and StyleDo not state the same idea twice with different words.
At this current moment in time, the study is ongoing.
The study is ongoing.
On the SAT: Answer choices stack synonyms: past history, final outcome, sudden surprise.
Match the sentence to the stated goal
Rhetorical SynthesisNotes questions give bullet points and a specific goal. The right answer uses the notes to accomplish exactly that goal.
Choosing an answer that is well written but ignores the stated goal.
Choosing the answer that fulfills the goal, such as emphasizing a contrast or introducing the topic to an unfamiliar reader.
On the SAT: These appear at the end of the Writing questions. The goal in the prompt, not style, decides the answer.
Use only the information in the notes
Rhetorical SynthesisBase your answer on the bullet points given. Do not add outside facts or assumptions.
Selecting an answer with a detail that never appears in the bullets.
Selecting the answer built entirely from the provided notes.
On the SAT: Wrong choices smuggle in details that are not supported by the notes.
Browse SAT Grammar by Topic
Sentence Boundaries
Where one sentence ends and the next begins: run-ons, comma splices, and fragments.
3 rules
Commas
The four comma jobs the SAT tests, and the one place a comma never belongs.
5 rules
Semicolons, Colons, and Dashes
The three heavier punctuation marks, when each one is right, and how the SAT swaps them to trap you.
4 rules
Apostrophes and Possessives
Its versus it's, plural versus possessive, and where the apostrophe lands.
4 rules
Subject-Verb Agreement
Matching a verb to its real subject when the SAT hides the subject behind a phrase.
4 rules
Verb Tense and Form
Choosing the tense the sentence's own time clues call for.
2 rules
Pronouns
Pronoun agreement, ambiguity, and the case forms the SAT loves to test.
3 rules
Modifiers
Keeping a describing phrase next to the thing it actually describes.
2 rules
Parallel Structure
Matching the form of items in a list or comparison.
2 rules
Transitions
Picking the transition word that fits the logic between two ideas.
3 rules
Concision and Style
Why the shortest clear option is usually the SAT's answer.
2 rules
Rhetorical Synthesis
The notes questions: using bullet points to hit a stated goal.
2 rules
How the Digital SAT Tests Grammar
The Reading and Writing section splits into four content areas, and two of them are grammar. Standard English Conventions covers the mechanical rules: where sentences end, how to punctuate them, and how verbs, pronouns, and modifiers have to agree. Expression of Ideas covers transitions and the notes-based synthesis questions, where the logic between ideas is the whole point. Together they make up close to half the section.
The good news is that this is the most learnable part of the entire SAT. Reading comprehension improves slowly, but grammar rules are finite and they repeat on every test. The same comma question, the same its versus it's, the same two-clause boundary, over and over. Once you can name the pattern a question is testing, you can answer it in seconds, and the section's adaptive difficulty stops working against you.
Notice that none of these questions ask you to define a term. The SAT will never say identify the subordinating conjunction. It shows you a sentence and four versions of one underlined piece, and exactly one follows the rule. So study by pattern, not by vocabulary. The examples on this page are written the way the test writes them for that reason.
Studying the Math section too?
Our Digital SAT Math formula sheet does for formulas what this page does for grammar: every formula you need, including the ones the College Board makes you memorize.
SAT Grammar Rules: Frequently Asked Questions
- How much of the SAT is grammar?
- Close to half of the Reading and Writing section. The Standard English Conventions questions test punctuation, sentence structure, verbs, pronouns, and modifiers, and the Expression of Ideas questions test transitions and rhetoric. Together that is roughly 40 to 50 percent of the section.
- What grammar is on the digital SAT?
- A fixed set of rules: sentence boundaries, commas, semicolons and colons, apostrophes, subject-verb agreement, verb tense, pronouns, modifiers, parallel structure, transitions, concision, and the notes-based rhetorical synthesis questions. This page covers every one of them.
- What is the most tested grammar rule on the SAT?
- Sentence boundaries. The single most common Writing question gives you two clauses and four ways to punctuate the split, a comma, a semicolon, a period, and a dash, and asks which is correct. Learn to tell an independent clause from a dependent one and this whole family of questions gets easy.
- Do I need to memorize grammar terms for the SAT?
- No. The SAT never asks you to name a rule. It asks you to apply one. You do not need to know the phrase subordinating conjunction; you need to hear that a clause cannot stand alone. Focus on recognizing patterns, not vocabulary.
- How do I get better at SAT grammar fast?
- Grammar is the most improvable part of the SAT because the rules are finite and repeat. Learn the dozen rule families on this page, then drill real questions until you spot each pattern on sight. A diagnostic shows which rules are costing you points so you study the right ones.