SAT Grammar Rules
What You Need to Know
SAT Grammar (the Writing/Language-style questions, including Digital SAT “Standard English Conventions”) tests whether you can recognize and fix errors in:
- Sentence structure (complete sentences, avoiding run-ons/fragments)
- Punctuation (commas, semicolons, colons, dashes, apostrophes)
- Agreement (subject–verb, pronoun–antecedent)
- Verb use (tense, mood, voice)
- Modifiers & parallelism (placing words where they logically belong)
- Pronouns (case, clarity, consistency)
- Conciseness & precision (clear, non-redundant wording)
Core idea: The SAT rewards rule-based choices. If you can name the grammar job being done (joining sentences, setting off extra info, showing possession, etc.), the correct answer usually becomes obvious.
Critical reminder: Most wrong answers are wrong for a specific rule reason (agreement error, comma splice, ambiguous pronoun, nonparallel structure). Don’t “pick what sounds right”—prove it.
Step-by-Step Breakdown
Use this quick process whenever you hit a grammar choice set.
Read the whole sentence (not just the underlined part).
- Your eyes need the subject, verb, and the boundaries of ideas.
Decide what kind of problem it is. (90% fall into these buckets)
- Sentence boundaries (run-on vs fragment): look for two complete sentences.
- Punctuation: commas/semicolons/colons/dashes.
- Agreement: subject–verb or pronoun–antecedent.
- Verb tense/consistency.
- Modifiers/parallelism.
- Pronoun case or clarity.
- Conciseness/redundancy.
For boundary/punctuation questions, identify independent vs dependent clauses.
- Independent clause = can stand alone.
- Dependent clause/phrase = cannot stand alone.
For agreement questions, strip the sentence to the core.
- Cross out prepositional phrases and interruptions:
- “The bouquet of roses smells…” (subject = bouquet)
- Cross out prepositional phrases and interruptions:
For modifier/parallelism, check structure symmetry.
- Lists should match grammar form: noun/noun/noun or verb-ing/verb-ing/verb-ing.
Eliminate answers that introduce new errors.
- The SAT loves “fix one thing, break another.” Re-check punctuation + agreement + pronouns.
Mini worked walk-through (common SAT pattern)
Sentence: “The researchers analyzed the data, and found a clear pattern.”
- After the comma: “and found…” is not an independent clause (no explicit subject).
- Fix: remove comma → “The researchers analyzed the data and found a clear pattern.”
Key Formulas, Rules & Facts
Sentence Boundaries (Fragments vs Run-ons)
| Rule | When to use | Notes |
|---|---|---|
| Independent clause stands alone | To test if something is a complete sentence | Must have a subject + finite verb + complete idea |
| Run-on = 2 independent clauses with no proper connector | If you see two complete sentences jammed together | Fix with period, semicolon, or comma + FANBOYS |
| Comma splice = comma between 2 independent clauses | If a comma is acting like a period | Fix like a run-on |
| Fragment = missing independent clause | If “sentence” can’t stand alone | Often caused by starting with which, because, although, that without a main clause |
Valid ways to join two independent clauses:
- Period: IC. IC.
- Semicolon: IC; IC.
- Comma + FANBOYS: IC, for/and/nor/but/or/yet/so IC.
- Subordinator (makes one dependent): Because/Although/While… DC, IC. OR IC because DC.
Warning: Comma + however/therefore is usually wrong if both sides are independent clauses. Use semicolon + however + comma or period + However,.
Commas (the SAT’s favorite punctuation)
| Comma rule | When to use | Quick check |
|---|---|---|
| Items in a list | A, B, and C | Keep list items grammatically parallel |
| Before FANBOYS joining 2 ICs | IC, and IC | If second half isn’t IC, usually no comma |
| After introductory phrase/clause | “After the storm, …” “While I was walking, …” | Intro chunk ends before main subject |
| Set off nonessential (extra) info | “My brother, who lives in Texas, …” | If you can remove it and sentence still identifies noun |
| Between coordinate adjectives | “a bright, sunny day” | If you can swap adjectives or add “and,” use comma |
| Avoid separating subject and verb | NOT: “The plan, is risky.” | SAT trap: unnecessary comma before verb |
Essential vs nonessential:
- Essential (needed to identify) → no commas: “Students who study pass.”
- Nonessential (extra detail) → commas: “My car, which is old, still runs.”
Semicolons
| Rule | When to use | Notes |
|---|---|---|
| Semicolon = period | Between two independent clauses | Both sides must stand alone |
| Use with conjunctive adverbs | IC; however, IC | Also: therefore, moreover, nevertheless, etc. |
SAT tell: If an answer uses a semicolon, check both sides for complete sentences.
Colons
| Rule | When to use | Notes |
|---|---|---|
| Colon introduces explanation/list/example | IC: explanation | Left side must be an independent clause |
| Common patterns | “One thing is clear: …” | What follows should directly explain/define |
No colon after: “such as,” “including,” “like” (often redundant).
Dashes and Parentheses
| Mark | When to use | Notes |
|---|---|---|
| Em dash — | Adds emphasis; sets off extra info | Like commas/parentheses but stronger |
| Parentheses ( ) | Side note, least emphasis | Don’t mix with dash/comma on the other side |
Consistency rule: If you open extra info with a dash, close with a dash (same for parentheses).
Apostrophes (Possession vs Plurals)
| Form | Meaning | Example |
|---|---|---|
| Singular possession: noun’s | belongs to one | the dog’s leash |
| Plural possession: plural s’ | belongs to many | the dogs’ leashes |
| It’s | it is / it has | It’s raining; It’s been fun |
| Its | possessive | The robot lost its arm |
Trap: Apostrophes do not make nouns plural.
Subject–Verb Agreement
| Rule | What to do | Common traps |
|---|---|---|
| Verb matches the subject, not nearby nouns | Identify the true subject | “A bouquet of roses smells…” |
| Singular indefinite pronouns often take singular verbs | each, either, neither, anyone, everyone | “Each of the players is…” |
| Compound subjects | usually plural with and | “Tom and Jerry are…” |
| Or/nor subjects | verb agrees with the closest subject | “Neither the teachers nor the student is…” |
Pronouns (Agreement, Case, Clarity)
| Pronoun rule | Use | SAT traps |
|---|---|---|
| Pronoun–antecedent agreement | singular ↔ singular | “Each student must bring his or her/their…” (SAT often prefers grammatically consistent; many tests accept singular they depending on context—avoid mismatch if options allow) |
| Clear antecedent | pronoun must clearly refer to one noun | Ambiguous “it/they/this” |
| Subject vs object case | I/he/she/we/they vs me/him/her/us/them | “between you and me” |
| Who vs whom | who = subject; whom = object | “Whom did you see?” (you saw whom) |
Quick case test: Replace with he/him.
- If “he” fits → who.
- If “him” fits → whom.
Verb Tense, Mood, and Voice
| Rule | What to check | Example fix |
|---|---|---|
| Consistency | keep tense consistent unless time shifts | “She walked in and sees…” → “walked… saw” |
| Sequence of tenses | past reporting often pushes past | “He said she was…” |
| Subjunctive (hypothetical) | use were for unreal | “If I were you…” |
| Conditional | would/could should match conditions | “If X happens, Y will…” (not “would” unless hypothetical) |
| Active vs passive | prefer active for clarity unless passive needed | “The team conducted the study” clearer than “The study was conducted” |
Modifiers (Placement and Logic)
| Rule | What to do | Trap example |
|---|---|---|
| Put modifiers next to what they modify | avoid confusion | “Running down the street, the backpack…” (backpack isn’t running) |
| Intro participial phrase must modify the subject right after it | check first noun after comma | “After reading the book, I…” |
Parallelism
| Rule | When to use | Example |
|---|---|---|
| Items in a list must match form | lists, comparisons, paired conjunctions | “to swim, to bike, and to run” |
| Paired conjunctions must be parallel | either/or, neither/nor, not only/but also | “not only studied but also worked” |
Comparisons
| Rule | What to check | Example |
|---|---|---|
| Compare like with like | person vs person, thing vs thing | “Her score is higher than mine (my score),” not “than me” (unless meaning is higher than me as a person) |
| Use than/as correctly | comparison markers matter | “as fast as,” “more than” |
Concision & Redundancy (Expression of ideas, but heavily grammar-adjacent)
| Goal | Prefer | Avoid |
|---|---|---|
| Short + precise | fewer words that keep meaning | wordy repeats (“in order to,” “due to the fact that”) |
| No redundancy | one clear phrase | “each and every,” “final outcome,” “past history” |
Examples & Applications
Example 1: Semicolon vs comma splice
Sentence: “The experiment failed, the team repeated it.”
- Both parts are independent clauses.
- Comma splice → wrong.
- Fix: “The experiment failed; the team repeated it.” OR “The experiment failed, so the team repeated it.”
Example 2: Essential vs nonessential clause
Sentence: “The paintings, that were stolen, were later recovered.”
- Clause “that were stolen” identifies which paintings → essential.
- Essential clauses don’t take commas.
- Fix: “The paintings that were stolen were later recovered.”
Example 3: Modifier placement (dangling modifier)
Sentence: “While hiking in the desert, the temperature rose quickly.”
- “While hiking…” should modify a person, not “temperature.”
- Fix: “While we were hiking in the desert, the temperature rose quickly.”
Example 4: Parallelism with paired conjunctions
Sentence: “She not only likes to paint but also sculpture.”
- Not parallel: “likes to paint” vs “sculpture.”
- Fix options:
- “She likes not only painting but also sculpting.”
- “She not only likes to paint but also likes to sculpt.”
Common Mistakes & Traps
Run-on/Comma Splice Blindness
- Wrong: Using a comma to join two complete sentences.
- Why wrong: A comma can’t do a period/semicolon’s job.
- Avoid: If both sides can stand alone, use .; or , + FANBOYS.
Misusing Semicolons
- Wrong: Putting a semicolon before a fragment.
- Why wrong: Semicolon requires an independent clause on both sides.
- Avoid: Do the “stand-alone test” on each side.
Commas Around Essential Information
- Wrong: “People, who exercise, live longer.”
- Why wrong: That implies all people exercise (nonessential meaning).
- Avoid: If the clause answers “which one(s)?,” it’s essential → no commas.
Unnecessary Commas Splitting Subject and Verb
- Wrong: “The reason for the delay, is unclear.”
- Why wrong: You can’t separate subject from its verb with a comma.
- Avoid: Find the core: “reason is.”
Agreement Errors Caused by Interruptions
- Wrong: “A list of rules are helpful.”
- Why wrong: Subject is “list” (singular), not “rules.”
- Avoid: Cross out “of rules” → “A list is helpful.”
Ambiguous Pronouns (“this,” “it,” “they”)
- Wrong: “The company cut costs, which improved profits. This was important.”
- Why wrong: “This” is vague—what exactly?
- Avoid: Replace with a noun: “This change was important.”
Faulty Parallelism
- Wrong: “The job requires attention to detail, writing clearly, and you must be organized.”
- Why wrong: List items don’t match form.
- Avoid: Make them all nouns/gerunds/infinitives.
Colon Misfires
- Wrong: “Her interests include: biology, chemistry, and physics.”
- Why wrong: Colon should follow an independent clause; “include” sets up a list already.
- Avoid: Either remove colon or rephrase: “Her interests include biology, chemistry, and physics.” OR “She has three interests: …”
Memory Aids & Quick Tricks
| Trick / mnemonic | What it helps you remember | When to use |
|---|---|---|
| Semicolon = Period | Both sides must be complete sentences | Any answer choice with a semicolon |
| FANBOYS | Valid coordinating conjunctions after a comma to join ICs | Fixing run-ons / boundary questions |
| “Remove it” test | Nonessential info can be removed without breaking meaning | Deciding commas around clauses/appositives |
| “He/him test” | who vs whom | Pronoun case questions |
| “Intro chunk, comma” | Add comma after introductory clause/phrase | Sentences starting with While/After/Although/etc. |
| “List = same shape” | Parallel structure | Lists, comparisons, either/or, not only/but also |
| “Colon = explanation” | Colon introduces what the first clause promises | Colon vs semicolon vs comma |
Quick Review Checklist
- Can you spot independent clauses quickly (subject + verb + complete idea)?
- If you see two ICs, are you choosing only: period / semicolon / comma+FANBOYS?
- Are commas used only for real jobs (lists, intro, nonessential info), not randomly?
- Do semicolons have IC on both sides?
- Does a colon come after an IC and introduce an example/list/explanation?
- Did you check subject–verb agreement by isolating the true subject?
- Do pronouns match their antecedents in number and have a clear reference?
- Are modifiers placed next to what they modify (no dangling/misplaced modifiers)?
- Are lists and paired conjunctions parallel?
- Did you prefer the most concise option that preserves meaning and grammar?
You’ve got this—treat every choice like a rule-check, not a vibe-check.