Mastering SAT and ACT: Complete grammar and punctuation rules - Part 1
Mar 12, 2025
Mastering SAT® and ACT®: Complete Grammar and Punctuation Rules
Scoring high on the SAT and ACT requires more than just strong reading and writing skills—it demands a solid grasp of grammar rules that are frequently tested. Each section in this blog provides clear explanations and examples to help you recognize common mistakes and choose the best answers with confidence.
I. Periods & Semicolons
Semicolon = Period
On the SAT and ACT, semicolons and periods function identically. If all other factors remain the same, you will never be asked to choose between them.
Semicolons and periods are used:
A. Used Between Two Complete Sentences
A semicolon or period must separate two independent clauses (complete sentences).
Correct: Paris is known for its historic landmarks. It attracts millions of tourists each year.
Correct: Paris is known for its historic landmarks; it is also a hub for fashion and art.B. Used Before Conjunctive Adverbs (e.g., however, therefore, moreover)
When a conjunctive adverb begins a new clause, it must be preceded by a semicolon.
Correct: Paris is famous for its museums; however, it also has a thriving modern art scene.
Correct: Paris is a major cultural center; therefore, many international artists choose to exhibit their work there.
Note: On the ACT, grammar questions testing "however" typically require a semicolon, whereas rhetoric questions often require a period.
Tip: Always read the entire sentence to its conclusion. Sentence boundary questions often trick test-takers by making the beginning of one sentence appear as part of the previous one. If you don’t read carefully, you might think the sentence is correct when it is actually a run-on.
Incorrect: Marie Curie made groundbreaking discoveries in radioactivity, she was the first woman to win a Nobel Prize.
Correct: Marie Curie made groundbreaking discoveries in radioactivity. She was the first woman to win a Nobel Prize.
2. Colons and Dashes
Colons and single dashes are used to introduce lists and explanations. On the SAT and ACT, they are considered grammatically identical, and you will never be asked to choose between them. However, colons tend to appear more frequently in test questions.
Unlike semicolons, colons and dashes can be followed by either a complete sentence or a fragment. While dashes create a stronger, more dramatic break, you do not need to focus on this distinction for testing purposes.
A colon or dash must always follow a complete sentence that logically sets up the information that follows.
A. Before a List
Incorrect: The research team studied a variety of: chemical reactions, energy transfers, and molecular structures.
Incorrect: The research team analyzed several key elements such as: temperature, pressure, and volume.
Correct: The research team focused on three main areas: chemical reactions, energy transfers, and molecular structures.
Correct: The research team focused on three main areas—chemical reactions, energy transfers, and molecular structures.
B. Before an Explanation
Correct: Many medical breakthroughs are the result of one key factor: years of rigorous experimentation.
Correct: Many medical breakthroughs are the result of one key factor—years of rigorous experimentation.
In the examples above, the second clause explains why medical breakthroughs occur. Because it directly clarifies the first statement, a colon or dash is acceptable.
When a colon or dash separates two sentences in an explanation, it functions similarly to a period or semicolon.
Note: On the digital SAT, questions that require separating two sentences often use colons instead of semicolons or periods, likely because fewer students are familiar with this rule.
3. Comma + FANBOYS
A. Comma + FANBOYS = Period = Semicolon
The coordinating conjunctions "and" and "but" are the most commonly tested on the SAT and ACT, while "so" and "yet" appear less frequently, and "or" and "nor" are rarely tested.
Correct: The research was groundbreaking, but some experts questioned its validity.
Correct: The research was groundbreaking, and it opened new possibilities for medical treatment.
B. Comma Splices
When two sentences are incorrectly joined by a comma, it creates a comma splice, which is always incorrect.
Tip-off: Look for comma + pronoun (e.g., it, they, she, he, one, you, I).
Incorrect: The study produced surprising results, it challenged previous assumptions.
Correct: The study produced surprising results. It challenged previous assumptions.
Correct: The study produced surprising results; it challenged previous assumptions.
C. Comma + FANBOYS + Verb = WRONG
When two clauses share the same subject, but the subject is omitted in the second clause, no comma is used before a FANBOYS conjunction.
Shortcut: If you replace comma + and/but with a period, and the second part doesn’t form a complete sentence, then the comma is incorrect.
Incorrect: The scientist published her findings, and presented them at a major conference.
Plug in: The scientist published her findings. Presented them at a major conference. (Incorrect)
Correct: The scientist published her findings and presented them at a major conference.
4. Commas & Dependent Clauses
Dependent clauses (also known as fragments) cannot stand alone as complete sentences. They begin with subordinating conjunctions, such as: although, because, when, until, while, since, before, and after.
Examples:
Because the experiment failed
When the results were analyzed
After the discovery was announced
A dependent clause must be attached to an independent clause to form a complete sentence. When the dependent clause comes first, it must be followed by a comma.
Incorrect: Because the research was inconclusive the scientists conducted further experiments.
Correct: Because the research was inconclusive, the scientists conducted further experiments.
Incorrect: Although the study had limitations it provided valuable insights.
Correct: Although the study had limitations, it provided valuable insights.
5. Transitional Words & Phrases
Many questions on the SAT and ACT test transitional words and phrases based on meaning rather than grammar. In these cases, all the answer choices will be grammatically correct, but only one will create the most logical connection between ideas.
There are three main types of transitions:
Continuers (e.g., furthermore, in addition, for example, then) add similar ideas, emphasize previous points, or indicate a sequence of events.
Cause-and-effect words (e.g., therefore, as a result, thus, consequently) show that one action/event caused another.
Contradictors (e.g., however, on the other hand, in contrast, nevertheless) signal opposing ideas.
Whenever you encounter a transition question, cross out or ignore the given transition and determine the logical relationship between the sentences (similar, opposite, or cause-and-effect) before selecting an answer.
Example:
The printing press revolutionized communication. ________, early versions of the technology were expensive and difficult to operate.
The two ideas contrast with each other, so a contradictor is needed.
Correct: The printing press revolutionized communication. However, early versions of the technology were expensive and difficult to operate.
Important Tips:
If two transitions have the same meaning (e.g., therefore and consequently), eliminate both—there can only be one correct answer. This shortcut is especially useful for the ACT.
If an OMIT/DELETE option is available (on the ACT) or an option without a transition appears, check it first—it is often correct.
6. Non-Essential Information
Non-essential information (a clause, phrase, or word) can be removed from a sentence without changing its fundamental meaning. Think of it as an interruption—the sentence should still make sense when that part is taken out.
There are three ways to set off non-essential information:
Two commas
Two dashes
Two parentheses
Only one type of punctuation can be used at a time; mixing them is incorrect. On the SAT and ACT, many wrong answer choices include this mistake.
A. Two Commas
Commas are the most common way to separate non-essential clauses. One comma must come before the clause, and one must come after.
Incorrect: Tokyo which is one of the busiest cities in the world, has a rich cultural history.
Incorrect: Tokyo, which is one of the busiest cities in the world has a rich cultural history.
Incorrect: Tokyo—which is one of the busiest cities in the world, has a rich cultural history.
Correct: Tokyo, which is one of the busiest cities in the world, has a rich cultural history. (Tokyo … has a rich cultural history.)
Single words, especially transitional words like however and though, can also be non-essential.
Incorrect: The museum is very popular. It is, however closed on Mondays.
Incorrect: The museum is very popular. It is however, closed on Mondays.
Correct: The museum is very popular. It is, however, closed on Mondays.
B. Two Dashes
Dashes can also be used to enclose non-essential information. Grammatically, they function the same way as commas in this context.
Correct: Tokyo—which is one of the busiest cities in the world—has a rich cultural history.
However, when a single word is non-essential, commas—not dashes—should be used.
Incorrect: The museum is very popular. It is—however—closed on Mondays.
Correct: The museum is very popular. It is, however, closed on Mondays.
C. Two Parentheses
Parentheses can also enclose non-essential information. This type of information is sometimes referred to as “parenthetical.”
Correct: Tokyo (which is one of the busiest cities in the world) has a rich cultural history.
A common mistake with parentheses is placing commas incorrectly before or after them. A comma before an opening parenthesis is never correct.
Incorrect: Tokyo, (which is one of the busiest cities in the world) has a rich cultural history.
A comma after a closing parenthesis is usually incorrect as well.
Incorrect: Tokyo (which is one of the busiest cities in the world), has a rich cultural history.
However, a comma may be required after a closing parenthesis in some cases, such as when it is needed for a FANBOYS conjunction.
Correct: Tokyo has been a major cultural center for centuries (since the Edo period, in fact), but it is also one of the most modern cities in the world.
7. Commas with Names & Titles
The use of commas around names and titles is a frequently tested concept on both the SAT and ACT. These questions assess whether the name or title is essential or non-essential to the sentence.
In general, there are only two correct ways to punctuate names and titles:
No commas → when the name or title is essential
Two commas (one before and one after) → when the name or title is non-essential
When a name or title appears in the middle of a sentence, a single comma before it is incorrect. Answer choices with this mistake can be eliminated immediately.
How to Determine If Commas Are Needed
To check whether commas are necessary, remove the name/title and see if the sentence still makes grammatical sense.
Example 1 (Essential - No Commas)
Incorrect: The team led by software engineer, Emma Carter, developed a new cybersecurity system.
Cross out: The team led by software engineer…developed a new cybersecurity system.
This does not make sense, meaning the name is essential and should not be separated by commas.
Correct: The team led by software engineer Emma Carter developed a new cybersecurity system.
Example 2 (Non-Essential - Two Commas)
Incorrect: The team led by a renowned software engineer Emma Carter developed a new cybersecurity system.
Cross out: The team led by a renowned software engineer…developed a new cybersecurity system.
The sentence still makes sense without the name, meaning the name is non-essential and should be set off by two commas.
Correct: The team led by a renowned software engineer, Emma Carter, developed a new cybersecurity system.
Exception: When a Comma is Required for Another Reason
In rare cases, a comma may be required after a name or title for a separate grammatical reason, such as marking the beginning of a new clause.
Correct: Led by software engineer Emma Carter, the team developed a new cybersecurity system.
8. Additional Comma Uses & Misuses
Commas SHOULD Be Used:
A. To Separate Items in a List
Incorrect: A balanced diet includes fruits vegetables whole grains and lean proteins.
Correct: A balanced diet includes fruits, vegetables, whole grains, and lean proteins.
Note: The comma before and + final item (Oxford comma) is optional and is not tested on the SAT or ACT.B. To Separate Adjectives Whose Order Could Be Reversed
Incorrect: The scientist presented a groundbreaking innovative discovery.
Correct: The scientist presented a groundbreaking, innovative discovery.
(You could also say "groundbreaking and innovative" or "innovative, groundbreaking.")
Note: Commas should also be used after introductory words or phrases (e.g., however, in the beginning, in fact), but this is not typically tested.
Commas Should NOT Be Used:
C. Before or After a Preposition (Frequently Tested)
Common prepositions: of, to, by, from, for, about, with, in, on, at
Incorrect: Leonardo da Vinci is considered one, of the greatest artists of all time.
Incorrect: Leonardo da Vinci is considered one of, the greatest artists of all time.
Correct: Leonardo da Vinci is considered one of the greatest artists of all time.D. Between Subjects and Verbs
This rule applies even when the subject is long.
Incorrect: The first successful heart transplant, was performed in South Africa in 1967.
Correct: The first successful heart transplant was performed in South Africa in 1967.E. Between Compound Items (Nouns, Verbs, Adjectives, etc. Linked by "and")
Shortcut: comma + and = period, so replace the comma with a period and check if there are two sentences.
Incorrect: The company is expanding its operations, and hiring new employees to meet demand.
Test: The company is expanding its operations. Hiring new employees to meet demand. (Incorrect!)
Correct: The company is expanding its operations and hiring new employees to meet demand.F. Before or After the Word "That"
Incorrect: The novel is a story, that explores themes of identity and resilience.
Incorrect: The novel is a story that, explores themes of identity and resilience.
Correct: The novel is a story that explores themes of identity and resilience.
If "that" is omitted, no comma should be used either.
Incorrect: The techniques, used in the research study led to groundbreaking results.
Correct: The techniques used (= the techniques that were used) in the research study led to groundbreaking results.G. Between Two Adjectives Whose Order Cannot Be Reversed
Incorrect: The chef prepared a delicious, Italian dish.
(You cannot say “Italian and delicious dish.”)
Correct: The chef prepared a delicious Italian dish.H. Between Adjectives and Nouns
Incorrect: The museum displayed several ancient, artifacts from different civilizations.
Correct: The museum displayed several ancient artifacts from different civilizations.
9. Apostrophes (Plural vs. Possessive)
A. Nouns
Apostrophes indicate possession (both singular and plural).
No apostrophe means plural only.
Rules for Forming Possessives:
Singular nouns: Add apostrophe + -s ('s).
Examples:
• The book’s cover = the cover of the book
• The teacher’s desk = the desk belonging to the teacher
• The dog’s leash = the leash of the dogRegular plural nouns: Add -s or -es + apostrophe (').
Examples:
• The books’ covers = the covers of multiple books
• The teachers’ lounge = the lounge for multiple teachers
• The dogs’ leashes = the leashes of multiple dogsIrregular plural nouns (do not end in -s): Add apostrophe + -s ('s).
Examples:
• The children’s toys = the toys belonging to the children
• The women’s conference = the conference for women
• The people’s choice = the choice made by the people
Tip: When two nouns appear together, the first noun usually takes an apostrophe to show possession.
Examples:
• The athlete’s performance review (a single athlete’s review)
• The athletes’ performance reviews (reviews for multiple athletes)
B. Pronouns
Unlike nouns, pronouns do not use apostrophes for possession.
It’s vs. Its
It’s = it is
Correct: The company announced it’s (it is) launching a new product.
Incorrect: The company announced its (it is) launching a new product.Its = possessive form of "it"
Correct: The cat licked its paws after eating.
Incorrect: The cat licked it’s paws after eating.
Note: "Its’" and "its’s" do not exist.
Test Strategy: On standardized tests like the ACT, the correct answer is almost always "its" because many students mistakenly associate apostrophes with possession.
They’re vs. Their vs. There
They’re = they are
Correct: They’re (they are) planning a trip to Italy.Their = possessive form of "they"
Correct: Their itinerary includes a visit to Rome.There = refers to a place
Correct: They arrived there an hour ago.
Quick Test: If you can replace the word with "they are," then they’re is correct.
Who’s vs. Whose
Who’s = who is
Correct: Who’s (who is) responsible for this project?Whose = possessive form of "who"
Correct: Do you know whose laptop this is?
Key Rule: "Whose" can be used for both people and things.
Correct: Paris is a city whose architecture is world-famous.
10. Pronouns & Nouns
A. Singular-Plural Agreement: Pronouns
Pronouns replace and refer back to nouns (antecedents).
Singular (people): he or she (Note: the SAT and ACT do not use the singular "they")
Singular (things): it, its, itself
Plural: they, them, their, themselves
The pronoun's antecedent may not always appear in the same sentence.
Incorrect: Scientist Marie Curie made groundbreaking discoveries in physics. It was awarded two Nobel Prizes.
Correct: Scientist Marie Curie made groundbreaking discoveries in physics. She was awarded two Nobel Prizes.
Common Test Trick: Pronoun agreement and apostrophes are often tested together.
Example (SAT/ACT-style question):
Question: Solar panels are installed on rooftops around the world; _______ designed to capture sunlight and convert it into electricity.
A) its
B) it’s
C) they’re
D) their
Answer: The referent solar panels is plural, so the correct choice is they’re (they are).
B. Singular-Plural Agreement: Nouns
A singular noun must match a singular verb, and a plural noun must match a plural verb.
Incorrect: The violin, the cello, and the piano is an essential part of an orchestra.
Correct: The violin, the cello, and the piano are essential parts of an orchestra.
C. People vs. Things
Who(m) = people
Incorrect: Nikola Tesla was an inventor which developed alternating current technology.
Correct: Nikola Tesla was an inventor who developed alternating current technology.Which = things
Incorrect: The car, who was parked outside, belongs to my neighbor.
Correct: The car, which was parked outside, belongs to my neighbor.
D. Who vs. Whom
A quick rule:
"Who" before a verb = correct
Incorrect: Jane Austen was a writer whom became famous for her novels.
Correct: Jane Austen was a writer who became famous for her novels."Whom" after a preposition = correct
Incorrect: Alexander Hamilton is a historical figure to who many scholars attribute early U.S. financial policies.
Correct: Alexander Hamilton is a historical figure to whom many scholars attribute early U.S. financial policies.
Tip: If you can replace it with he/she, use who. If you can replace it with him/her, use whom.
Mastering these grammar rules is key to achieving a high score on the SAT and ACT, but knowing the rules is just the first step. At North American Tutors, our expert instructors provide personalized coaching to help students apply these concepts effectively and gain confidence in their test-taking skills. Sign up today and take the next step toward your dream score!
By the way, our new blog with the remaining rules is now live! Check it out at Mastering SAT and ACT Grammar and Punctuation - Part 2.
