SAT Grammar Rules to Memorize: A Complete Guide to Mechanical Grammar

SAT grammar can feel intimidating, but most of it comes down to a predictable set of mechanical rules. The SAT is not usually testing whether a sentence “sounds fancy.” It is testing whether a sentence is grammatically complete, clear, logical, and properly punctuated.

For students, this is actually good news. Many SAT grammar questions become much easier once you memorize the core rules and learn what the test is really asking.

On the digital SAT, grammar questions usually ask: “Which choice completes the text so that it conforms to the conventions of Standard English?” That means the correct answer must follow the standard rules of sentence structure, punctuation, verb tense, agreement, modifiers, and pronoun use.

This guide breaks down the most important SAT grammar rules students should know.

1. A Complete Sentence Needs a Subject and a Verb

A complete sentence must have a subject and a main verb.

Correct:
The researcher published her findings.

Subject: researcher
Verb: published

Incorrect:
The researcher who studied sleep patterns in teenagers.

This is not a complete sentence because “who studied sleep patterns in teenagers” describes the researcher, but the sentence never tells us what the researcher did.

Correct:
The researcher who studied sleep patterns in teenagers published her findings.

A common SAT trick is to hide the subject inside a long phrase.

Example:
The results of the experiment on memory and sleep were surprising.

Subject: results
Verb: were

Do not let the phrase “of the experiment on memory and sleep” distract you. The subject is not “sleep.” The subject is “results.”

2. Independent Clauses vs. Dependent Clauses

An independent clause can stand alone as a complete sentence.

Example:
The student reviewed her notes.

A dependent clause cannot stand alone because it begins with a word that makes it incomplete.

Example:
Although the student reviewed her notes.

This leaves us waiting for the rest of the idea.

Correct:
Although the student reviewed her notes, she still needed more practice.

Common dependent-clause words include although, because, when, while, since, if, after, before, unless, and even though.

The SAT loves to test whether students can recognize a complete thought.

Incorrect:
Because the data was incomplete.

Correct:
Because the data was incomplete, the scientists repeated the experiment.

3. Do Not Join Two Complete Sentences With Only a Comma

This is called a comma splice.

Incorrect:
The exam was difficult, the students stayed focused.

Both sides are complete sentences:
The exam was difficult.
The students stayed focused.

A comma alone is too weak to connect them.

Correct options:

The exam was difficult, but the students stayed focused.

The exam was difficult; the students stayed focused.

The exam was difficult. The students stayed focused.

The exam was difficult: the students stayed focused.

Use a comma plus a coordinating conjunction, a semicolon, a period, or a colon.

4. FANBOYS Conjunctions Need a Comma When Joining Two Complete Sentences

FANBOYS stands for for, and, nor, but, or, yet, so.

When one of these words connects two complete sentences, use a comma before it.

Correct:
The assignment was long, but the student finished it.

Complete sentence 1: The assignment was long.
Complete sentence 2: The student finished it.

Incorrect:
The assignment was long but the student finished it.

However, do not automatically put a comma before every FANBOYS word.

Correct:
The student read the chapter and took notes.

There is no comma because “took notes” does not have its own subject. The sentence is not joining two complete sentences.

5. Semicolons Connect Two Closely Related Complete Sentences

A semicolon works like a soft period. Both sides must be complete sentences.

Correct:
The first trial failed; the second trial produced accurate results.

Incorrect:
The first trial failed; producing accurate results in the second trial.

The second part is not a complete sentence, so the semicolon is wrong.

A semicolon can often replace a period, but it cannot replace a comma randomly.

6. Colons Introduce Explanations, Examples, or Lists

A colon should come after a complete sentence.

Correct:
The experiment required three materials: a beaker, a thermometer, and a timer.

The part before the colon is complete: “The experiment required three materials.”

Incorrect:
The experiment required: a beaker, a thermometer, and a timer.

This is wrong because “The experiment required” is not complete.

Colons can also introduce an explanation.

Correct:
The result was unexpected: the control group improved more than the experimental group.

The second clause explains why the result was unexpected.

7. Dashes Can Work Like Parentheses, Colons, or Commas

Dashes often set off extra information or create emphasis.

Correct:
The scientist’s discovery — a new method for measuring ocean temperature — changed the field.

If the extra information interrupts the sentence, use two dashes.

Correct:
The novel’s narrator — unreliable, anxious, and deeply observant — shapes the reader’s understanding of the plot.

If the extra information comes at the end, use one dash.

Correct:
The team made one major mistake — they ignored the early data.

On the SAT, dashes are often interchangeable with commas or parentheses, but the punctuation must be balanced.

Incorrect:
The scientist’s discovery — a new method for measuring ocean temperature, changed the field.

Do not open with a dash and close with a comma unless the sentence structure requires it. Usually, match punctuation around interrupting information.

8. Nonessential Information Needs Commas

Nonessential information can be removed without destroying the basic meaning of the sentence.

Correct:
My brother, who lives in Boston, is visiting this weekend.

The phrase “who lives in Boston” adds extra information. It is not necessary to identify which brother if the speaker only has one brother.

Essential information should not be surrounded by commas.

Correct:
The student who submitted the essay early received feedback first.

Here, “who submitted the essay early” is necessary because it tells us which student.

The SAT often tests whether a description is essential or extra.

Incorrect:
The author, who wrote the anonymous letter was later identified.

Correct:
The author who wrote the anonymous letter was later identified.

If the phrase identifies which person or thing, do not use commas.

9. Appositives Rename a Noun

An appositive is a noun phrase that renames another noun.

Correct:
Toni Morrison, the author of Beloved, won the Nobel Prize in Literature.

“The author of Beloved” renames Toni Morrison.

If the appositive is extra information, use commas.

Correct:
The planet Venus, the second planet from the Sun, has a thick atmosphere.

If the appositive is essential, do not use commas.

Correct:
The poet Maya Angelou wrote I Know Why the Caged Bird Sings.

“Maya Angelou” identifies which poet.

10. Subject-Verb Agreement: Singular Subjects Need Singular Verbs

A singular subject takes a singular verb.

Correct:
The student studies every night.

A plural subject takes a plural verb.

Correct:
The students study every night.

The SAT often separates the subject from the verb with extra words.

Incorrect:
The list of books are on the desk.

Correct:
The list of books is on the desk.

The subject is “list,” not “books.”

More examples:

Incorrect:
The effects of sleep deprivation is serious.

Correct:
The effects of sleep deprivation are serious.

Subject: effects
Verb: are

Incorrect:
The collection of poems reveal the author’s grief.

Correct:
The collection of poems reveals the author’s grief.

Subject: collection
Verb: reveals

11. Ignore Prepositional Phrases When Finding the Subject

Prepositional phrases often begin with words like of, in, on, with, for, from, by, about, between, among, and under.

Example:
The box of old photographs was found in the attic.

Subject: box
Verb: was

Do not match the verb to the noun inside the prepositional phrase.

Incorrect:
The box of old photographs were found in the attic.

Correct:
The box of old photographs was found in the attic.

12. “Each,” “Every,” and “One” Are Singular

These words usually take singular verbs.

Correct:
Each of the students has a notebook.

Correct:
Every book on the shelf belongs to the library.

Correct:
One of the experiments was successful.

Even if the sentence contains a plural noun nearby, the subject is singular.

Incorrect:
Each of the researchers have a different theory.

Correct:
Each of the researchers has a different theory.

13. Collective Nouns Are Usually Singular

Words like team, group, committee, audience, family, and class are usually treated as singular on the SAT.

Correct:
The team is preparing for the competition.

Correct:
The committee has reached a decision.

14. Verb Tense Must Match the Timeline

Verb tense tells when something happens. The SAT often gives context clues like dates, time periods, or surrounding verbs.

Correct:
In 1928, Alexander Fleming discovered penicillin.

The year 1928 tells us the verb should be past tense.

Correct:
Today, scientists study the long-term effects of sleep deprivation.

“Today” suggests present tense.

Correct:
By the time the researchers published the paper, they had completed three trials.

Use “had completed” for an action that happened before another past action.

The key question is: when did this happen?

15. Keep Verb Tense Consistent Unless the Time Changes

Incorrect:
The scientist collected the samples and analyzes the results.

Correct:
The scientist collected the samples and analyzed the results.

Both actions happened in the past.

But if the time changes, the tense can change.

Correct:
The scientist collected the samples in 2020 and now analyzes them in a new study.

The words “in 2020” and “now” justify the shift.

16. Pronouns Must Clearly Refer to a Specific Noun

A pronoun should have a clear antecedent, which is the noun it refers to.

Correct:
Maria finished the essay before she submitted it.

“She” refers to Maria.
“It” refers to the essay.

Incorrect:
When Maria gave Anna her notebook, she smiled.

Who smiled? Maria or Anna? The pronoun is unclear.

Correct:
When Maria gave Anna the notebook, Anna smiled.

On the SAT, clarity beats style. If a pronoun could refer to more than one noun, the sentence should be rewritten.

17. Pronouns Must Agree in Number

Singular nouns need singular pronouns. Plural nouns need plural pronouns.

Incorrect:
Each student must bring their calculator.

Traditionally, the SAT often prefers:

Correct:
Each student must bring his or her calculator.

However, because “they” is increasingly accepted as a singular pronoun in modern English, students should pay close attention to the answer choices. The SAT usually avoids controversial pronoun questions and focuses more on clarity and agreement.

Safer SAT-style version:
All students must bring their calculators.

18. “It’s” vs. “Its”

This one is mechanical and worth memorizing.

It’s = it is
Its = belonging to it

Correct:
It’s raining outside.
Translation: It is raining outside.

Correct:
The company changed its policy.
Meaning: the policy belongs to the company.

Incorrect:
The bird spread it’s wings.

Correct:
The bird spread its wings.

19. “They’re,” “Their,” and “There”

They’re = they are
Their = belonging to them
There = a place or situation

Correct:
They’re studying for the SAT.

Correct:
Their books are on the table.

Correct:
There are three options.

20. “Who” vs. “Whom”

Who is used for the subject of a verb.
Whom is used for the object of a verb or preposition.

Correct:
Who wrote the article?

Correct:
To whom should I send the email?

Quick trick: if you could replace it with “he” or “she,” use who. If you could replace it with “him” or “her,” use whom.

Who wrote it?
He wrote it.

To whom did you speak?
I spoke to him.

That said, “whom” is less commonly tested now than punctuation, agreement, and sentence boundaries.

21. Modifiers Must Be Placed Next to What They Describe

A modifier is a describing phrase. On the SAT, modifiers must be logically placed.

Incorrect:
Walking through the museum, the ancient sculpture impressed the student.

This sounds like the sculpture was walking through the museum.

Correct:
Walking through the museum, the student was impressed by the ancient sculpture.

The phrase “walking through the museum” describes the student, so “student” should come right after the comma.

Another example:

Incorrect:
Covered in chocolate, the child ate the strawberries.

This sounds like the child was covered in chocolate.

Correct:
The child ate the strawberries covered in chocolate.

22. Introductory Phrases Usually Need Commas

When a sentence begins with an introductory phrase, use a comma before the main sentence.

Correct:
After finishing the assignment, the student took a break.

Correct:
In the early twentieth century, many artists experimented with abstraction.

Correct:
Because the results were unclear, the researchers repeated the study.

Short introductory phrases sometimes do not require commas, but on the SAT, a comma is often preferred when it improves clarity.

23. Parallel Structure: Items in a List Must Match

Parallel structure means that items in a list or comparison should have the same grammatical form.

Incorrect:
The program teaches students to read carefully, writing clearly, and how to revise effectively.

Correct:
The program teaches students to read carefully, write clearly, and revise effectively.

All three items now match:
read
write
revise

Another example:

Incorrect:
The scientist was known for her patience, curiosity, and analyzing data carefully.

Correct:
The scientist was known for her patience, curiosity, and careful analysis of data.

Or:

Correct:
The scientist was known for observing patiently, questioning curiously, and analyzing data carefully.

24. Comparisons Must Be Logical

Compare people to people, things to things, and actions to actions.

Incorrect:
The novels of James Baldwin are more complex than Ernest Hemingway.

This compares novels to a person.

Correct:
The novels of James Baldwin are more complex than the novels of Ernest Hemingway.

Or:

Correct:
James Baldwin’s novels are more complex than Ernest Hemingway’s.

Another example:

Incorrect:
Unlike London, the weather in Los Angeles is mild.

This compares a city to weather.

Correct:
Unlike the weather in London, the weather in Los Angeles is mild.

25. Apostrophes Show Possession or Contraction

Singular possession usually takes apostrophe + s.

Correct:
The student’s notebook was missing.

Plural possession usually takes s + apostrophe.

Correct:
The students’ notebooks were missing.

That means:

The student’s notebook = one student owns the notebook.
The students’ notebook = multiple students share one notebook.
The students’ notebooks = multiple students own multiple notebooks.

Do not use apostrophes just to make nouns plural.

Incorrect:
The researcher collected three sample’s.

Correct:
The researcher collected three samples.

26. Commas Do Not Separate a Subject From Its Verb

Incorrect:
The discovery of several ancient tools, changed the archaeologists’ theory.

Correct:
The discovery of several ancient tools changed the archaeologists’ theory.

Do not place a comma between the subject and verb.

Subject: discovery
Verb: changed

Even if the subject is long, do not separate it from the verb.

27. Commas Do Not Separate a Verb From Its Object

Incorrect:
The study revealed, a surprising connection between sleep and memory.

Correct:
The study revealed a surprising connection between sleep and memory.

Verb: revealed
Object: connection

Do not put a comma between an action and the thing receiving the action.

28. Use Commas Between Items in a List

Correct:
The student packed pencils, a calculator, and a snack.

The SAT usually uses the Oxford comma, which is the comma before “and” in a list of three or more items.

Correct:
The course covers algebra, grammar, and reading comprehension.

29. Use Commas Between Coordinate Adjectives

Coordinate adjectives equally describe the same noun. If you can put “and” between them, use a comma.

Correct:
The student wrote a thoughtful, detailed essay.

Thoughtful and detailed essay = makes sense.

Do not use a comma when the adjectives build on each other.

Correct:
She bought a new math book.

“New and math book” does not make sense, so no comma.

30. Transition Words Must Match the Logic

SAT grammar sometimes overlaps with transitions. A transition must show the correct relationship between ideas.

Use however, nevertheless, although, despite this for contrast.

Example:
The first experiment failed. However, the researchers gained useful information.

Use therefore, thus, consequently, as a result for cause and effect.

Example:
The data was incomplete. Therefore, the team delayed its conclusion.

Use for example, for instance, specifically to introduce examples.

Example:
Many animals use camouflage. For example, the walking stick insect resembles a twig.

Use moreover, furthermore, additionally to add information.

Example:
The program improves reading fluency. Moreover, it helps students build confidence.

The SAT is not asking which transition “sounds smart.” It is asking which transition matches the relationship between the ideas.

31. “Although” and “However” Are Not Used the Same Way

Although is a subordinating conjunction. It creates a dependent clause.

Correct:
Although the assignment was difficult, the student completed it.

However is a transition. It usually connects two complete ideas with a period or semicolon before it and a comma after it.

Correct:
The assignment was difficult. However, the student completed it.

Correct:
The assignment was difficult; however, the student completed it.

Incorrect:
The assignment was difficult, however the student completed it.

32. “Because” Explains Why

Because introduces a reason.

Correct:
The student improved because she practiced consistently.

Correct:
Because she practiced consistently, the student improved.

Do not use “because” if the sentence needs a contrast or result instead.

Incorrect:
The student practiced consistently because she still struggled on the exam.

Better:
The student practiced consistently, but she still struggled on the exam.

33. Use “Fewer” for Countable Things and “Less” for Noncount Things

Use fewer when you can count the noun.

Correct:
fewer mistakes
fewer students
fewer assignments

Use less for amounts that are not usually counted individually.

Correct:
less water
less time
less stress

SAT questions do not focus heavily on this, but it is a useful mechanical rule.

34. Use “Amount” for Noncount Nouns and “Number” for Countable Nouns

Correct:
A large number of students attended the workshop.

Correct:
A small amount of water remained in the bottle.

Students can be counted, so use number. Water is treated as a mass noun, so use amount.

35. Use “Between” for Two and “Among” for Three or More

Correct:
The choice between the two courses was difficult.

Correct:
The teacher divided the supplies among the four groups.

This rule is less common on the SAT but still worth knowing.

36. Avoid Redundancy

The SAT often rewards concise, non-repetitive writing.

Incorrect:
The reason the student improved was because she practiced.

Correct:
The student improved because she practiced.

Incorrect:
The final outcome of the experiment was unexpected.

Correct:
The outcome of the experiment was unexpected.

“Final outcome” is often redundant because an outcome is already a result.

37. Avoid Wordiness

The correct SAT answer is often the clearest and most concise grammatically correct option.

Wordy:
Due to the fact that the student was tired, she made mistakes.

Better:
Because the student was tired, she made mistakes.

Wordy:
The author is someone who uses imagery frequently.

Better:
The author uses imagery frequently.

Do not choose the shortest answer automatically, but if two answers are grammatically correct, the clearer and more concise one is usually better.

38. Make Sure the Sentence Has a Clear Main Idea

Sometimes SAT grammar questions are really testing sentence structure. A sentence can contain many descriptions, but it still needs a clear main idea.

Confusing:
The scientist, known for her research on memory, which influenced later studies, and whose work changed psychology.

This sentence has no main verb.

Correct:
The scientist, known for her research on memory, influenced later studies and changed psychology.

39. Watch for “Which” vs. “That”

Use “that” for essential information.

Correct:
The book that changed her perspective was written in 1962.

Use “which” for nonessential information, usually after a comma.

Correct:
The book, which was written in 1962, changed her perspective.

The SAT may not always directly test this distinction, but it helps with comma questions.

40. Possessive Nouns Before Gerunds

A gerund is an -ing word acting as a noun.

More formal:
The teacher appreciated the student’s asking thoughtful questions.

Less formal:
The teacher appreciated the student asking thoughtful questions.

This is not one of the most common SAT rules, but students aiming for top scores may benefit from recognizing it.

41. “Like” vs. “Such As”

Use “such as” to introduce examples.

Correct:
Many subjects, such as biology and chemistry, require strong study habits.

“Like” is often used for comparison.

Correct:
A whale, like a dolphin, is a mammal.

On the SAT, “such as” is usually safer when listing examples.

42. Sentence Fragments Are Incomplete Thoughts

A fragment is missing a subject, a verb, or a complete idea.

Fragment:
Although the student studied for three hours.

Complete:
Although the student studied for three hours, she still felt nervous.

Fragment:
The novel about a family living during the war.

Complete:
The novel about a family living during the war won several awards.

Fragment:
Running through the park before sunrise.

Complete:
Running through the park before sunrise, the athlete prepared for the race.

43. Run-On Sentences Need Proper Boundaries

A run-on sentence occurs when two complete sentences are joined incorrectly.

Incorrect:
The student wanted to improve she practiced every day.

Correct:
The student wanted to improve, so she practiced every day.

Correct:
The student wanted to improve; she practiced every day.

Correct:
The student wanted to improve. She practiced every day.

The SAT calls these “boundaries” questions because they test whether students know where one complete thought ends and another begins.

44. “Where” Should Refer to Places

Incorrect:
The book describes a theory where sleep improves memory.

A theory is not a place.

Correct:
The book describes a theory in which sleep improves memory.

Correct:
The book describes a theory that explains how sleep improves memory.

Use “where” for actual locations.

Correct:
The library is where the students met.

45. “When” Should Refer to Time

Incorrect:
The process when cells divide is called mitosis.

Correct:
The process by which cells divide is called mitosis.

Use “when” for time.

Correct:
The moment when the results appeared was exciting.

46. Titles and Names Often Need Precise Punctuation

When a title or name is essential to identify a person or thing, do not use commas.

Correct:
The novel Beloved was written by Toni Morrison.

Do not write:

Incorrect:
The novel, Beloved, was written by Toni Morrison.

This implies there is only one novel in the world or that the title is extra information.

But if the title is extra information, commas are appropriate.

Correct:
Toni Morrison’s novel Beloved, which was published in 1987, won the Pulitzer Prize.

47. Dates Often Need Commas

Correct:
On July 20, 1969, astronauts landed on the Moon.

Correct:
In July 1969 astronauts landed on the Moon.

Month + day + year usually uses commas. Month + year does not need a comma.

Correct:
The book was published in March 2020.

48. Use “Affect” as a Verb and “Effect” as a Noun

Affect usually means to influence.

Correct:
Sleep affects memory.

Effect usually means result.

Correct:
Sleep has a powerful effect on memory.

Quick trick:
Affect = action
Effect = end result

49. “Then” vs. “Than”

Than is used for comparison.

Correct:
The second passage is shorter than the first.

Then is used for time or sequence.

Correct:
The student reviewed grammar and then practiced math.

50. The Best SAT Grammar Strategy: Find the Core Sentence

When a grammar question feels confusing, strip the sentence down to its core.

Example:
The collection of rare manuscripts, along with several letters and sketches, was donated to the museum.

Core sentence:
The collection was donated.

That is why “was” is correct, not “were.”

This strategy helps with subject-verb agreement, punctuation, modifiers, and sentence boundaries.

Final SAT Grammar Checklist

Before choosing an answer, ask:

Is the sentence complete?

Are two complete sentences joined correctly?

Does the subject agree with the verb?

Is the verb tense logical?

Does every pronoun clearly refer to one noun?

Is the modifier next to the thing it describes?

Are commas used only where they are needed?

Is extra information properly set off?

Are lists and comparisons parallel?

Is the answer clear, concise, and logical?

SAT grammar is not about memorizing every grammar term in the English language. It is about recognizing the patterns the test repeats.

Once students understand sentence boundaries, punctuation, agreement, modifiers, tense, pronouns, and parallel structure, the grammar section becomes much more mechanical and much less mysterious.

At My Total Tutor, we teach students not just to memorize rules, but to understand how sentences work. When students learn to see the structure underneath the words, they become stronger test-takers, clearer writers, and more confident thinkers.