Mastering SAT Grammar: 9 Most-Tested Rules to Know

A clear breakdown of the grammar rules the SAT tests most with correct-vs-incorrect examples and a quick tip for each, so you can spot and fix errors fast.

📖 5 min read

SAT Writing & Language

Updated 2026

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Mastering grammar on the SAT is one of the fastest ways to raise your Writing & Language score. Below are the rules the test returns to again and again, each with the common trap, a correct-vs-incorrect example, and a quick tip. They may feel tricky at first, but once the pattern clicks, they become second nature.

Subject-Verb Agreement

The subject and verb must agree in number (singular or plural). The SAT loves to slip a phrase between them to blur the match.

Common trap: an interrupting phrase separates the subject from its verb.

The team of players are ready for the game.

✓

The team of players is ready for the game.

Tip: Cross out the phrase between the subject and verb ("of players"), then match the verb to the true subject ("team").

Pronoun Agreement & Clarity

A pronoun must agree in number with the noun it replaces and refer clearly to one specific noun — no ambiguity about who "they" or "it" is.

Common trap: a pronoun with no clear antecedent, or a number mismatch.

Maria told Jen that she had passed.

(Who passed?)

✓

Maria told Jen, "You passed."

(Clear antecedent.)

Tip: For every pronoun, ask "which noun does this point to?" If more than one answer is possible, rewrite for clarity.

🏴 Flagged for review: the live page uses "Every student should bring his or her book" and marks "their" as incorrect. On the Digital SAT, singular "their" is widely accepted and this construction isn't tested as an error — consider updating this example. Left unchanged here pending your call.

Sentence Fragments & Run-Ons

A fragment is missing a subject or verb (or is a stray dependent clause). A run-on jams two complete sentences together without proper punctuation.

Common trap: a long clause that feels complete but isn't, or two sentences fused with just a comma.

Because I finished my homework.

(fragment)

I finished my homework I went to the store.

(run-on)

✓

Because I finished my homework, I went to the store.

Tip: Every sentence needs a subject and a verb. Join two independent clauses with a period, a semicolon, or a comma + FANBOYS conjunction.

Comma Usage

Commas separate list items, join independent clauses (with a conjunction), and set off non-essential information.

Common trap: misplacing commas in compound sentences, or failing to fence off a non-essential clause on both sides.

✓

In a list: I bought apples, oranges, and bananas.

✓

Before a conjunction: She studied hard, but she didn't pass.

✓

Non-essential: The dog, which is very friendly, loves fetch.

Tip: Remove the phrase between the two commas. If the sentence still makes sense, the commas are correctly placed.

Apostrophes: Possessives vs. Contractions

Apostrophes mark possession or stand in for missing letters in a contraction. The pronoun pairs (its/it's, your/you're, their/they're) are the SAT's favorites.

Common trap: confusing the possessive pronoun with its contraction.

The dog wagged it's tail.

(= "it is" tail)

✓

The dog wagged its tail. • It's a sunny day.

(= it is)

Tip: Replace "it's" with "it is." If the sentence still works, the apostrophe is right. If not, you need the possessive "its."

Parallel Structure

Items in a list or comparison must share the same grammatical form — all gerunds, all infinitives, all nouns.

Common trap: mixing forms partway through a list.

She likes running, to swim, and biking.

✓

She likes running, swimming, and biking.

Tip: When you see a list or comparison, check that every element takes the same form (verb, noun, or adjective).

Modifier Placement

A modifier must sit directly next to the word it describes. An introductory phrase modifies the noun that immediately follows the comma.

Common trap: a dangling modifier that ends up describing the wrong noun — often an unintentionally funny one.

Running through the park, the flowers looked beautiful.

(the flowers ran?)

✓

Running through the park, I noticed the flowers looked beautiful.

Tip: After an introductory "-ing" phrase, the very next word must be the one doing the action.

Verb Tense Consistency

Tenses stay consistent within a sentence or passage unless the meaning clearly signals a shift in time.

Common trap: sliding between past and present within a single sentence.

She ran to the store and buys milk.

✓

She ran to the store and bought milk.

Tip: Lock onto the sentence's main tense and only switch when there's a clear reason to mark a different time.

Commonly Confused Words

The SAT tests near-homophones that sound alike but do different grammatical jobs. Know the pair and the quick test for each.

PAIR	THE DIFFERENCE	QUICK TEST
Affect / Effect	Affect = verb (to influence); Effect = noun (a result)	Can you put "the" in front? → effect
Then / Than	Then = time/sequence; Than = comparison	Comparing two things? → than
Who / Whom	Who = subject (does the action); Whom = object (receives it)	Answer with "he" → who; "him" → whom

Tip: Learn each pair with its one-line test, then practice in context — spotting them becomes automatic.

WHY IT MATTERS

From Rules to Real Results

Our approach goes beyond drilling rules, we teach students to understand and apply these concepts in ways that stick, improving both SAT scores and everyday writing. Master the most-tested rules and you lift your Writing & Language score and build skills that carry through college and beyond.

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