SAT Grammar Rules
What You Need to Know
SAT “grammar” questions test Standard English Conventions: you’re fixing sentences so they’re grammatical, clear, and consistent. Most correct answers follow a small set of repeatable rules—especially sentence boundaries, punctuation, agreement, and modifiers.
Big idea: choose the option that is grammatically correct and most concise/precise without changing the intended meaning.
Critical reminder: On SAT grammar, “sounds right” is unreliable. Use rules and quickly test the structure (subject/verb, clause boundaries, modifier targets).
High-yield categories
Sentence boundaries: fragments vs run-ons; how to join clauses
Punctuation: commas, semicolons, colons, dashes, apostrophes
Agreement: subject–verb and pronoun–antecedent
Pronoun case: who/whom, I/me, they/them, etc.
Modifiers: placement; dangling/misplaced modifiers
Parallelism: lists, comparisons, paired constructions
Verbs: tense, consistency, mood, voice
Conciseness & precision: redundancy, wordiness, vague pronouns
Transitions & logic: however/therefore/for example; sentence placement
Step-by-Step Breakdown
Use this quick decision process for most SAT grammar questions:
Identify what’s being tested.
Look for clues: punctuation changes, pronoun swaps, verb changes, transition words, longer/shorter choices.
Find the core sentence.
Mentally strip extra phrases between commas/dashes/parentheses.
Locate the main subject and main verb.
Check clause boundaries (the #1 trap).
If you see two full sentences (two independent clauses) next to each other, you need:
Period OR
Semicolon OR
Comma + FANBOYS (for, and, nor, but, or, yet, so) OR
Subordinating word (because, although, while, when, since, etc.) to make one clause dependent.
Apply the specific rule.
Agreement: match subject ↔ verb and pronoun ↔ antecedent.
Pronoun case: decide if the pronoun is acting as subject or object.
Modifiers: place the modifier next to what it describes.
Parallelism: ensure same grammatical form.
Prefer the most concise choice that is fully correct.
Eliminate redundancy and wordiness, but don’t cut needed meaning.
Do a 3-second read for meaning and tone.
Make sure transitions are logical and references are clear (no “this/that/which” with unclear antecedent).
Mini worked walkthrough (how to “see” a run-on)
Sentence: “The study was small, the results were surprising.”
“The study was small” = independent clause.
“the results were surprising” = independent clause.
Comma alone can’t join them → fix with semicolon / period / comma+FANBOYS.
Key Formulas, Rules & Facts
Sentence boundaries & clause joining (highest yield)
Structure | Correct fixes | Notes |
|---|---|---|
Independent + Independent | ; OR . OR , + FANBOYS | Comma alone = comma splice (wrong). |
Independent + Dependent | Usually no comma if dependent is second | “I left because it was late.” |
Dependent + Independent | Comma after dependent clause | “Because it was late, I left.” |
Fragment (no main verb or incomplete clause) | Add missing subject/verb or attach to nearby clause | Watch “which/that” fragments. |
Rule of thumb: If both sides can stand alone as sentences, you need ; . or ,FANBOYS.
Commas (what they do and don’t do)
Comma use | When it’s correct | Quick test |
|---|---|---|
Items in a list | 3+ items | “A, B, and C” |
Before FANBOYS | Only when both sides are independent clauses | Read each side alone. |
After introductory clause/phrase | Often after long intro; always after dependent intro clause | “After the meeting, …” |
Setting off nonessential info | For extra info that can be removed | Name appositives, “which” clauses |
Around interrupters | However, therefore, in fact, etc. | “The plan, however, failed.” |
Comma traps
Do not separate subject from verb: “The group of students, are…” (wrong)
Do not separate verb from object: “She presented, the data…” (wrong)
Semicolons, colons, dashes
Punctuation | What it can connect | Must have… | Common SAT use |
|---|---|---|---|
Semicolon (;) | Independent clause + independent clause | Full sentence on both sides | Swap with a period. |
Colon (:) | Independent clause + explanation/list | Complete independent clause before colon | Use for definitions, lists, dramatic explanation. |
Dash (—) | Like colon or parentheses | Whatever matches the sentence structure | Emphasis; set off an interruption. |
Colon rules (very testable):
Left of the colon must be a complete sentence.
After a colon, you can have a list, a phrase, or a full clause.
Essential vs nonessential information
Type | Punctuation | Common clue |
|---|---|---|
Essential (restrictive) | No commas | Needed to identify the noun |
Nonessential (nonrestrictive) | Commas (or dashes/parentheses) | Extra detail; sentence still works without it |
That vs which (SAT-style):
that often introduces essential info (no commas).
which often introduces nonessential info (commas).
Apostrophes (possession vs plural)
Form | Meaning | Example |
|---|---|---|
Singular possessive | add ’s | the dog’s collar |
Plural possessive | add ’ (if already plural -s) | the dogs’ collars |
Its | possessive pronoun | its color |
It’s | it is / it has | it’s raining |
Subject–verb agreement
Rule: the verb agrees with the true subject, not with words in between.
High-yield traps:
Prepositional phrases: “The bouquet of roses smells…” (bouquet = singular)
Appositives/interruptions: “The leader, along with her advisors, is…”
Either/neither: usually singular (“Neither of the options is…”)
Each/every: singular (“Each of the students has…”)
Compound subjects:
With and → plural (“Tea and coffee are…”) unless treated as one unit (“Mac and cheese is…”, rare)
With or/nor → agree with the nearest subject (“Either the teachers or the student is…”)
Pronoun agreement & clarity
Issue | Correct rule | SAT trap |
|---|---|---|
Pronoun–antecedent agreement | singular antecedent → singular pronoun | “Each student must bring his or her/their…” (SAT often accepts singular “their” in modern usage, but choose clearest/most consistent option.) |
Pronoun clarity | pronoun must clearly refer to one noun | “When Jim met Bob, he…” (ambiguous) |
Reflexives | only when subject = object | “She taught herself” vs “He and myself” (wrong) |
Pronoun case (I/me, who/whom)
Function | Use | Quick test |
|---|---|---|
Subject | I, he, she, we, they, who | Replace with “he” / “she” |
Object (verb or preposition) | me, him, her, us, them, whom | Replace with “him” / “her” |
Examples:
“Between you and me” (object of preposition)
“The researcher who won…” (who = subject of won)
“The researcher whom the committee praised…” (whom = object of praised)
Modifiers (placement matters)
Rule: a modifier should be placed right next to what it modifies.
Common modifier types:
Introductory modifiers: must describe the subject immediately after.
Wrong: “Running down the street, the backpack bounced.”
Right: “Running down the street, I felt my backpack bounce.”
Only/just/even: place them carefully to match meaning.
Parallelism
Pattern | Must match | Example |
|---|---|---|
Lists | same grammatical form | “valued for its speed, accuracy, and reliability” |
Comparisons | compare like with like | “Her score is higher than mine (not ‘me’ as a subject)” |
Paired words | keep structures aligned | “not only X but also Y”; “either X or Y” |
Verb tense, consistency, mood, and voice
Keep tense consistent unless time changes.
Past narrative → stay past.
Present perfect (“has/have done”) = started in past, continues/relevant now.
Conditional mood (would, could) only if truly hypothetical.
Active voice is usually clearer/concise, but passive can be correct if logical.
Concision & diction (what SAT rewards)
Choose… | Over… | Why |
|---|---|---|
concise, direct wording | redundancy (“in order to,” “due to the fact that”) | SAT prefers simplest correct. |
precise verbs/nouns | vague (“does things,” “stuff,” “things”) | Clarity/meaning. |
logical comparisons | mismatched comparisons | Avoid illogical meaning. |
Transitions & logical connectors
Common transition meanings:
Contrast: however, nevertheless, on the other hand
Cause/effect: therefore, thus, consequently
Addition: moreover, furthermore
Example: for instance, for example
Sequence: then, subsequently
Rule: pick the transition that matches the relationship between sentences, not the one that “sounds academic.”
Examples & Applications
Example 1: Fixing a run-on
Original: “The team finished the experiment, the results surprised everyone.”
Two independent clauses.
Correct fixes include:
“The team finished the experiment; the results surprised everyone.”
“The team finished the experiment, and the results surprised everyone.”
Key insight: comma alone can’t join two complete sentences.
Example 2: Essential vs nonessential clause
Sentence: “The paintings, that were stolen last year, were recovered.”
If the sentence means only the stolen paintings (essential), remove commas and use that:
“The paintings that were stolen last year were recovered.”
If it means all the paintings and the theft is extra detail (nonessential), use commas and often which:
“The paintings, which were stolen last year, were recovered.”
Key insight: commas change meaning; decide whether the detail identifies the noun.
Example 3: Modifier placement
Wrong: “Nearly after finishing the novel, Maya wrote a review.”
“Nearly” is misplaced (it suggests she almost finished).
Better: “After nearly finishing the novel, Maya wrote a review.”
Key insight: place modifiers next to the word they’re modifying.
Example 4: Parallelism in lists
Wrong: “The workshop teaches students to code, designing games, and how to debug.”
Better parallel options:
“The workshop teaches students to code, design games, and debug.” (all base verbs)
“The workshop teaches students coding, game design, and debugging.” (all gerunds)
Key insight: once you spot a list, force consistent grammar.
Common Mistakes & Traps
Comma Splice (Run-on with a comma)
Wrong: joining two independent clauses with just a comma.
Why wrong: comma can’t do a semicolon/period’s job.
Fix: use ;, ., or , + FANBOYS.
Fragment from “which/that” or missing verb
Wrong: “The plan, which efficient and cheap.”
Why wrong: no complete clause.
Fix: add a verb (“which was efficient…”) or attach properly.
Separating subject and verb with commas
Wrong: “The reasons for the change, are unclear.”
Why wrong: interrupts the core grammar.
Fix: remove comma: “reasons … are.”
Agreement errors with distracting phrases
Wrong: “A collection of rare coins are valuable.”
Why wrong: subject is “collection” (singular).
Fix: “collection … is.”
Pronoun ambiguity (“this/that/it/they” with unclear antecedent)
Wrong: “Companies reduced hours, which upset workers.” (What does “which” refer to?)
Why wrong: unclear reference.
Fix: name the idea: “a decision that upset workers.”
Misplaced/dangling modifiers
Wrong: “To improve the score, the test was retaken.” (Test can’t intend.)
Why wrong: modifier lacks a real doer.
Fix: “To improve the score, the student retook the test.”
Faulty parallelism (especially with paired words)
Wrong: “The policy is not only expensive but also it is inefficient.”
Why wrong: mismatched structures.
Fix: “not only expensive but also inefficient.”
Bad colon usage
Wrong: “My favorite fruits are: apples and oranges.”
Why wrong: colon must follow a complete sentence; “are” dangles.
Fix: “My favorite fruits are apples and oranges.” OR “I like these fruits: apples and oranges.”
Memory Aids & Quick Tricks
Trick / Mnemonic | Helps you remember | When to use |
|---|---|---|
“IC + IC needs ; . or ,FANBOYS” | How to join two independent clauses | Sentence boundary questions |
FANBOYS (for, and, nor, but, or, yet, so) | Legit coordinating conjunctions for comma joins | Choosing between comma vs semicolon |
“Colon = because/namely” | Colon introduces explanation/list | Colon vs semicolon decisions |
“Semicolon = period” | Both sides must be complete sentences | Testing semicolon choices |
“Delete test” for commas | Nonessential info can be removed | Which/that, appositives |
“Preposition = object case” | After prepositions use me/him/whom | Between/with/to/by questions |
“Nearest noun with or/nor” | Agreement in either/or constructions | Subject–verb agreement traps |
“Same game” for parallelism | Keep same grammatical form | Lists, not only/but also, either/or |
Quick Review Checklist
Can you spot independent clauses fast and avoid comma splices?
Do you know the 4 legal ways to join two independent clauses (.; ,FANBOYS)?
Are commas used only for lists, intros, interrupters, and nonessential info (not between subject–verb)?
Do you test colons by checking for a complete sentence before the colon?
Do verbs agree with the true subject, ignoring prepositional phrases?
Do pronouns match their antecedents in number and remain unambiguous?
Can you choose who vs whom using the he/him substitution test?
Do modifiers sit next to the word they describe (no dangling intros)?
Are lists and paired structures parallel?
When choices are all grammatical, do you pick the most concise without losing meaning?
You’ve got this—treat each question like a mini proof, and the “right” answer becomes obvious.