SAT/ACT Prep•Grammar Guide

SAT/ACT Grammar Overview

These are the technical grammar rules that show up most often on SAT and ACT English questions: commas, semicolons, colons, dashes, apostrophes, and the distinctions the test makers like to hide in answer choices.

CommasSemicolonsColonsDashesApostrophesQuick test-day tips

Commas

Use commas when the sentence structure requires a pause, separation, or extra information.

Correct uses

Between two independent clauses joined by a FANBOYS conjunction: I wanted to go, but I didn’t have enough money.
After an introductory phrase or clause: After the movie, we got ice cream.
Around nonessential information: My brother, a dentist, drove fast.
Between items in a list: I bought apples, oranges, kiwis, and bananas.
Between equal adjectives: It was a long, exhausting day.
Before a dependent clause that follows a complete sentence: She kept studying, even though she was exhausted.

Do not use commas

Between a subject and verb: My brother is a dentist.
Between compound verbs: I ran and cried.
Before that or because when the sentence does not need a pause.

Wrong: My brother, is a dentist.

Right: The car, which I bought last year, still runs perfectly.

Semicolons

Use a semicolon to join two closely related complete sentences.

Correct: She trained hard; she won the race.

Incorrect: Because she trained hard; she won the race.

If you can replace the semicolon with a period and still have two full sentences, it usually works.

With transitions like however, therefore, or moreover, use a semicolon before the transition and a comma after it.

Example: I was tired; however, I kept working.

Colons

Use a colon after a full sentence to introduce a list, example, explanation, or clarification.

Correct: He had one goal: success.

Correct: She brought three things: a notebook, a pencil, and her determination.

The clause before the colon must be a complete sentence.

Dashes

Dashes add emphasis or interruption. Think of them as drama punctuation.

Use two dashes to set off extra information: My dog—who hates baths—hid under the bed.
Use a dash for a sharp turn or emphasis: She finally reached the summit—it was breathtaking.
A dash can replace a colon for stronger emphasis: There’s only one rule—never give up.

Use either two dashes or none. Do not mix one dash with one comma.

Wrong: My dog—who hates baths, hid under the bed.

Right: My dog, who hates baths, hid under the bed.

Apostrophes

Type	Example
Singular possession	the dog’s toy
Plural possession	the dogs’ toys
Irregular plural possession	the children’s books

Use apostrophes in contractions too: it’s, they’re, who’s, you’re.

Possessive pronouns do not take apostrophes: its, theirs, yours, hers, his, ours, whose.

Common traps

Decades: 1990s, not 1990’s
Plurals: CDs, not CD’s
Pronouns: its is possessive; it’s means it is

Quotation Marks

Quotation marks are less common on the SAT, but the punctuation rules are standard.

Periods and commas go inside the quotation marks.
Colons and semicolons go outside the quotation marks.

Examples: She said, “Let’s go.” / She called it “weird”; I called it “art.”

Parentheses

Use parentheses for minor extra information that the sentence can survive without.

Example: The plan (which he proposed last week) was approved.

The SAT may offer commas, dashes, or parentheses as alternatives. Any of them can work if the sentence stays grammatically consistent.

Hyphens

Hyphens usually join compound adjectives when they come before a noun.

a well-known author
a five-year-old child
a world-renowned singer

Do not force the hyphen when the phrase comes after the noun.

Wrong: The child is five-years-old.

Right: The child is five years old.

Ellipses and Question Marks

These are rare on the SAT.

Ellipses usually show omission or a pause.
Question marks end direct questions, but the test may hide them inside sentence fragments.

Trickiest SAT Punctuation Distinctions

If you have...	Use...	Example
Two full sentences, no conjunction	Semicolon	She was tired; she still worked.
Two full sentences plus FANBOYS	Comma	She was tired, but she still worked.
Full sentence plus list or explanation	Colon	She brought three things: water, food, and hope.
Sentence interrupted for emphasis	Two dashes	The truth—that he lied—shocked everyone.
Equal adjectives before a noun	Comma	a long, tiring day
Possession of a plural noun	Apostrophe after the s	the students’ grades

Mini Tips

Never use a semicolon with and, but, or other coordinating conjunctions.
Comma + which, but usually no comma + that.
When punctuation comes in pairs, match both sides. If the sentence opens with a dash or comma interruption, it must close the same way.

Want help applying these rules to real test questions?

Grammar rules matter most when you can spot them quickly inside a passage. That part gets much easier with targeted practice and feedback.

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