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:

1. Identify what’s being tested.

   • Look for clues: punctuation changes, pronoun swaps, verb changes, transition words, longer/shorter choices.

2. Find the core sentence.

   • Mentally strip extra phrases between commas/dashes/parentheses.
   • Locate the main subject and main verb.

3. 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.

4. 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.

5. Prefer the most concise choice that is fully correct.

   • Eliminate redundancy and wordiness, but don’t cut needed meaning.

6. 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)

Rule of thumb: If both sides can stand alone as sentences, you need ; . or ,FANBOYS.

Commas (what they do and don’t do)

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

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

That vs which (SAT-style):

• that often introduces essential info (no commas).
• which often introduces nonessential info (commas).

Apostrophes (possession vs plural)

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

Pronoun case (I/me, who/whom)

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

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)

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

1. 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.

2. 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.

3. 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.”

4. Agreement errors with distracting phrases

   • Wrong: “A collection of rare coins are valuable.”
   • Why wrong: subject is “collection” (singular).
   • Fix: “collection … is.”

5. 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.”

6. 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.”

7. 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.”

8. 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

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.