The SAT tests a specific, limited set of grammar rules — the same ones every time. Learn these and grammar questions become the most reliably scoreable part of the whole test.
Sentence Structure
The most tested area on the digital SAT. Know the difference between a complete sentence, a run-on, and a fragment — and how to fix each one.
Sentence Structure
Run-On Sentences
Two complete sentences incorrectly joined together.
A run-on happens when two independent clauses (complete sentences) are joined without the right punctuation.
Four ways to fix a run-on:
Use a period to make two sentences
Use a semicolon (;) between them
Use a comma + FANBOYS (for, and, nor, but, or, yet, so)
Use a subordinating conjunction (because, although, when, since)
Wrong → Right
She studied all night, she still felt unprepared.
She studied all night; she still felt unprepared.
She studied all night, yet she still felt unprepared.
The comma splice — joining two independent clauses with only a comma — is the most common error the SAT tests. A comma alone is never enough.
Sentence Structure
Sentence Fragments
A group of words that looks like a sentence but isn't complete.
A fragment is missing a subject, a main verb, or both — or it starts with a subordinating word that leaves the thought incomplete.
Common fragment types:
No subject: "Ran to the finish line." (Who ran?)
No verb: "The scientist with twenty years of experience."
Dependent clause alone: "Because the results were unexpected."
Wrong → Right
Although the study produced useful findings.
Although the study produced useful findings, the methodology was questioned.
Sentence Structure
Subordinating Conjunctions
Words that make one clause dependent on another.
Subordinating conjunctions (because, although, since, when, while, unless, if, after, before) turn a clause into a dependent one — it can no longer stand alone.
The rule: A dependent clause must be attached to an independent clause. If it stands alone, it's a fragment.
Structure
[Dependent clause], [Independent clause].
[Independent clause] [dependent clause].
Note: when the dependent clause comes first, use a comma. When it comes second, no comma needed.
Punctuation
The SAT tests a small set of punctuation rules repeatedly. Master these and you'll get every punctuation question right.
Punctuation
Semicolons ( ; )
Functions exactly like a period — joins two complete sentences.
The only rule: Both sides of a semicolon must be independent clauses (complete sentences that could stand alone).
Correct use
The experiment failed; the team redesigned the protocol.
Wrong use
The experiment failed; forcing the team to start over.
("forcing the team to start over" is not a complete sentence)
Don't confuse with: Semicolons are also used to separate items in a list when the items themselves contain commas — but this rarely appears on the SAT.
Punctuation
Colons ( : )
Introduces a list, explanation, or elaboration.
The rule: What comes before a colon must be a complete sentence. What comes after can be a list, a phrase, or another sentence.
Correct
She packed three things: a notebook, a pen, and a book.
Wrong
She packed: a notebook, a pen, and a book.
("She packed" is not a complete sentence on its own)
Tip: If you can say "namely" or "which is/are" after the blank and it makes sense, a colon is probably correct.
Punctuation
Dashes ( — )
Adds emphasis, interrupts, or sets off a parenthetical.
Two uses on the SAT:
1. Single dash — introduces an explanation or emphasis (similar to a colon):
Example
There was one problem — no one had the key.
2. Paired dashes — surround a non-essential interruption (similar to parentheses):
Example
The study — which took three years — produced surprising results.
The SAT test: If a dash opens a parenthetical, the closing punctuation must also be a dash (not a comma or parenthesis).
Punctuation
Commas
The most nuanced punctuation mark — and the most tested.
When to use a comma:
After an introductory phrase or clause: After the rain, the streets were clear.
Before a coordinating conjunction (FANBOYS) joining two complete sentences: I wanted to go, but it was too late.
Around non-essential (parenthetical) information: The book, which was published in 1984, became a classic.
Between items in a list: red, white, and blue
When NOT to use a comma:
Between a subject and its verb: The tall student, won the award.
Between a verb and its object: She noticed, the error.
Before a subordinating conjunction at the end of a sentence: She stayed, because she wanted to help.
Punctuation
Apostrophes
Possession and contractions — two completely different uses.
Possession:
Singular noun: the dog's bone (the bone belonging to the dog)
it's = it is / it has. its = possessive (no apostrophe)
they're = they are. their = possessive. there = place
you're = you are. your = possessive
Classic SAT trap
The committee made it's decision.
The committee made its decision.
Punctuation
Parentheses ( ( ) )
Sets off non-essential, explanatory background information.
The Punctuation Match Rule: Information inside parentheses must be completely non-essential to the grammatical framework of the main sentence. If you remove it, the sentence must still stand perfectly on its own.
Crucial SAT Rule: You cannot mix and match parenthetical boundary markers. If an interruption opens with a parenthesis, it must close with a parenthesis (not a comma or a dash).
Wrong
The aurora borealis (a spectacular natural light display — occurs most frequently in high-latitude regions.
Right
The aurora borealis (a spectacular natural light display) occurs most frequently in high-latitude regions.
Punctuation
Hyphens ( - ) vs. Dashes
Joins compound words together; never used to separate clauses.
Do not confuse hyphens with em-dashes! A hyphen (-) is small and connects words inside a modifier. An em-dash (—) is long and acts like a structural punctuation wall (similar to a colon or parenthesis).
Compound Modifiers: Use a hyphen when combining two words to describe a single noun that immediately follows.
Examples
The nineteenth-century novel was lengthy.
They collected data using a well-designed paradigm.
Note: If the description comes *after* the noun, you usually do not need the hyphen (e.g., "The paradigm was well designed").
Subject-Verb & Noun Agreement
The SAT deliberately hides the true subject to trick you into agreeing the verb with the wrong noun.
Agreement
Subject-Verb Agreement
The verb must match its true subject — not the nearest noun.
The SAT's favourite trick: Inserting a prepositional phrase or relative clause between the subject and verb.
Wrong
The impact of the new policies were significant.
Right
The impact of the new policies was significant.
Subject = "impact" (singular). "policies" is inside a prepositional phrase — ignore it.
The move: Cross out everything between commas or inside prepositional phrases. Match the verb to what's left.
Agreement
Tricky Subjects
Some subjects look plural but are singular — and vice versa.
Always singular (take singular verb):
Each, every, either, neither, one
Anyone, everyone, someone, no one
Collective nouns used as a unit: the team wins, the committee decides
Compound subjects with "or/nor": verb agrees with the nearer subject.
Example
Neither the students nor the teacher was prepared.
("teacher" is closer to the verb → singular)
Agreement
Noun Consistency
Nouns used to refer to a group must stay consistent (singular or plural).
The pattern: "A student should bring their notebook" — the SAT now accepts singular "they" for gender neutrality, but the number must still be consistent across the sentence.
Wrong
Each student must submit their assignments and then get their grade reviewed by a teacher before they leave.
(mixing "each student" [singular] with "they" can create ambiguity — the SAT tests whether the pronoun logically refers to its antecedent)
Pronouns
Pronouns must agree with and clearly refer to their antecedents. Vague, ambiguous, or mismatched pronouns are tested regularly.
Pronouns
Pronoun-Antecedent Agreement
A pronoun must match its antecedent in number and gender.
Wrong
The company announced they would expand.
Right
The company announced it would expand.
("company" is singular → "it")
Indefinite pronouns are singular: everyone, someone, anyone, each, either, neither → use his or her or restructure. The SAT now also accepts singular they for gender-neutral reference.
Pronouns
Ambiguous Pronoun Reference
A pronoun must clearly refer to exactly one antecedent.
If a pronoun could logically refer to more than one noun, it's ambiguous — and wrong on the SAT.
Ambiguous
When Maria told Sarah the news, she was surprised.
(Who was surprised — Maria or Sarah?)
Fixed
When Maria told Sarah the news, Sarah was surprised.
Pronouns
Pronoun Case (I vs. Me, Who vs. Whom)
Use subject pronouns for subjects; object pronouns for objects.
Subject (doing the action)
Object (receiving the action)
I, he, she, we, they, who
me, him, her, us, them, whom
The "who/whom" trick: Replace with he/him. If "he" sounds right → who. If "him" sounds right → whom.
Test
"Who/Whom did you call?" → You called him. → Whom did you call?
Modifiers
A modifier must be placed next to — and logically refer to — the word it's describing.
Modifiers
Misplaced Modifiers
A modifier placed too far from the word it describes.
Wrong
She almost drove her children to school every day.
("almost" modifies "drove" — she nearly drove but didn't?)
Right
She drove her children to school almost every day.
The move: Read the modifier and ask: what is it describing? Then check that the word it should describe is immediately next to it.
Modifiers
Dangling Modifiers
An introductory phrase that doesn't logically connect to the subject of the main clause.
When a sentence starts with a participial phrase, the subject of the main clause must be the one doing that action.
Wrong (dangling)
Walking through the park, the flowers were beautiful.
(The flowers weren't walking — this modifier "dangles" with no logical subject)
Right
Walking through the park, she admired the beautiful flowers.
Quick test: After a comma following an introductory phrase, the very next noun must be the one doing the action in that phrase.
Parallelism & Other Rules
Items in a list or comparison must use the same grammatical form.
Parallelism
Parallel Structure
All items in a list or pair must use the same grammatical form.
Wrong
She likes running, to swim, and to cycle.
Right
She likes running, swimming, and cycling.
Also check comparisons:
Wrong
His salary is higher than his colleague.
Right
His salary is higher than his colleague's.
(comparing salary to salary, not salary to colleague)
Usage
Verb Tense Consistency
Tense must stay consistent unless there's a logical reason to change.
If a passage is written in the past tense, all verbs should stay in the past tense unless the text is clearly referring to something that happened before or after.
Wrong
The scientist conducted the experiment and then publishes her results.
Right
The scientist conducted the experiment and then published her results.
Tip: Read the surrounding sentences to establish the intended tense, then make the underlined verb match.
Concision
Wordiness & Redundancy
The SAT rewards concise, clear writing — eliminate redundancy.
If two answer choices are grammatically correct, choose the shorter, clearer one. The SAT values concision.
Common redundancies to eliminate:
"past history" → "history" (history is already past)
"end result" → "result"
"the reason why is because" → "the reason is that" or "because"
"in order to" → "to"
"at this point in time" → "now"
Quick Reference — Punctuation Rules
Period / Semicolon
Both sides must be complete sentences. Interchangeable in most cases. Never use a comma alone here.
Colon
Left side must be a complete sentence. Right side introduces a list, explanation, or elaboration.
Dash (paired)
Surrounds non-essential info like parentheses. If one dash opens it, the other must close it — not a comma.
Comma + FANBOYS
Only correct way to join two independent clauses with a comma. FANBOYS = for, and, nor, but, or, yet, so.
its vs it's
it's = it is. its = possessive. When in doubt, expand it: if "it is" makes sense, use the apostrophe.
Dangling modifier test
After the opening phrase + comma, the very next noun must be the thing doing the action in that phrase.