SAT Reading & Writing · Standard English Conventions
Grammar & Punctuation
SAT-W-CONV-01
Teaching Notes
v1 · 2026.05
The SAT tests a small, fixed set of grammar and punctuation rules — the same handful of rules over and over. Once you know which mark does which job, most questions become 15-second decisions. This note covers the four punctuation marks the SAT actually tests (commas, semicolons, colons, dashes), the six grammar rules behind almost every error, and a quick decision reference for the test itself.
Punctuation — when each mark does its job
The SAT tests four punctuation marks. Each has a specific role; the test rewards students who know exactly when to use each one and — just as importantly — when not to. The marks, in rough order of how often they appear:
Comma ,
Separates parts of a sentence. Five main jobs.
Semicolon ;
Joins two complete sentences. Acts like a period.
Colon :
Introduces a list or explanation.
Dash —
Adds emphasis. Often replaces commas or colons.
Commas — five jobs
The comma is the SAT's favorite punctuation mark. It has five distinct uses, and most "comma errors" on the test fall into one of two categories: missing a comma where you need one, or adding a comma where you don't. Knowing the five legitimate uses tells you which is which.
① Join two complete sentences with FANBOYS
When a coordinating conjunction (For, And, Nor, But, Or, Yet, So) joins two complete sentences, put a comma before the conjunction.
EXAMPLE 1
✗ The recipe called for cinnamon but I had only nutmeg.
Two complete sentences joined by "but" — needs a comma before the conjunction.
✓ The recipe called for cinnamon, but I had only nutmeg.
EXAMPLE 2 — NO COMMA WHEN THE SECOND PART ISN'T A COMPLETE SENTENCE
✗ The recipe called for cinnamon, and used nutmeg as a substitute.
"Used nutmeg as a substitute" has no subject — it's not a complete sentence. No comma needed before "and."
✓ The recipe called for cinnamon and used nutmeg as a substitute.
② Separate items in a series
When listing three or more items, put a comma between each. The "Oxford comma" before the final "and" is preferred but not always required; the SAT uses it consistently.
EXAMPLE 1
✗ She packed sandwiches apples and water for the hike.
Three items in a list — separate with commas.
✓ She packed sandwiches, apples, and water for the hike.
EXAMPLE 2 — DON'T ADD A COMMA AFTER THE LAST ITEM
✗ Sandwiches, apples, and water, were all she packed.
The comma after "water" wrongly separates the subject from the verb.
✓ Sandwiches, apples, and water were all she packed.
③ After an introductory phrase
When a phrase comes before the main clause and sets the scene, follow it with a comma. This applies to time/place phrases, dependent clauses ("Although...," "When..."), and most participial openings.
EXAMPLE 1
✗ After the storm passed we walked outside.
"After the storm passed" is an introductory clause — needs a comma before the main sentence.
✓ After the storm passed, we walked outside.
EXAMPLE 2
✗ Determined to finish the marathon Olivia trained for six months.
"Determined to finish the marathon" is a participial phrase introducing the subject.
✓ Determined to finish the marathon, Olivia trained for six months.
④ Around non-essential information
Information that could be removed without changing the sentence's basic meaning gets surrounded by commas (or dashes — see below). Information the sentence needs to make sense gets no commas.
EXAMPLE 1 — NON-ESSENTIAL (USE COMMAS)
✓ My oldest brother, who lives in Chicago, is visiting next week.
"Who lives in Chicago" adds extra info — the sentence still makes sense without it. The commas signal that.
EXAMPLE 2 — ESSENTIAL (NO COMMAS)
✓ The brother who lives in Chicago is visiting next week.
"Who lives in Chicago" identifies which brother — it's essential. No commas.
⑤ When NOT to use a comma
Three SAT-favorite mistakes — knowing these saves you from the test's most common comma traps:
EXAMPLE 1 — DON'T SEPARATE SUBJECT FROM VERB
✗ The students in the back row, were whispering.
Never put a single comma between a subject ("students") and its verb ("were").
✓ The students in the back row were whispering.
EXAMPLE 2 — DON'T USE A COMMA BEFORE "BECAUSE"
✗ She left early, because she felt unwell.
"Because" usually shouldn't take a comma before it — it tightly links the reason to the action.
✓ She left early because she felt unwell.
The single most common SAT comma error
Comma splice: using a comma alone to join two complete sentences. A comma is too weak for that job — you need either a semicolon, a period, or a comma plus a FANBOYS conjunction.
✗ The lecture ran long, students started leaving.
✓ The lecture ran long; students started leaving.
✓ The lecture ran long, so students started leaving.
✓ The lecture ran long. Students started leaving.
Semicolons — one job
The semicolon does exactly one thing on the SAT: it joins two complete sentences without a conjunction. Think of it as a "soft period." If you can replace it with a period and still have two complete sentences, the semicolon is correct.
EXAMPLE 1
✓ The road was closed; we took the long way home.
Both sides ("The road was closed" / "we took the long way home") are complete sentences. The semicolon links them and signals a close relationship between the two ideas.
EXAMPLE 2 — WITH "HOWEVER" OR OTHER CONJUNCTIVE ADVERBS
✗ The exam was difficult, however, most students passed.
"However" is not a FANBOYS conjunction — a comma alone can't join the two sentences. Use a semicolon before "however."
✓ The exam was difficult; however, most students passed.
EXAMPLE 3 — WHAT GOES WRONG WHEN ONE SIDE ISN'T COMPLETE
✗ Although it was raining; we went hiking.
"Although it was raining" is a fragment, not a complete sentence. Use a comma instead.
✓ Although it was raining, we went hiking.
Colons — introduce something
A colon introduces what follows it: a list, an explanation, a definition, or a quote. The rule that catches most students: what comes before the colon must be a complete sentence on its own. What comes after can be anything — a single word, a phrase, a list, another sentence.
EXAMPLE 1 — INTRODUCING A LIST
✓ He brought three things to the interview: a resume, a portfolio, and a smile.
"He brought three things to the interview" is a complete sentence; the colon introduces the list of what those things were.
EXAMPLE 2 — INTRODUCING AN EXPLANATION
✓ The reason was simple: the printer had run out of ink.
First half is a complete sentence; the colon introduces the explanation.
EXAMPLE 3 — WHEN A COLON DOESN'T WORK
✗ The three primary colors are: red, blue, and yellow.
"The three primary colors are" isn't a complete sentence — it's a fragment. Either drop the colon entirely, or rewrite the lead-in.
✓ The three primary colors are red, blue, and yellow.
✓ Three colors are primary: red, blue, and yellow.
Dashes — emphasis or interruption
The em dash (—) has two main jobs on the SAT, and both overlap with marks you already know:
Replace commas around non-essential info — same job, more emphasis.
Replace a colon when introducing an explanation or list, in a slightly less formal way.
The SAT's favorite trap with dashes: they have to be used in matching pairs. If you open a non-essential phrase with a dash, you must close it with a dash. Don't mix a dash with a comma.
EXAMPLE 1 — DASHES INSTEAD OF COMMAS (MORE EMPHATIC)
✓ My oldest brother — who lives in Chicago — is visiting next week.
Same meaning as the comma version, but the dashes set off the inserted phrase more dramatically.
EXAMPLE 2 — DASH INSTEAD OF COLON
✓ He brought three things to the interview — a resume, a portfolio, and a smile.
Like a colon, the dash introduces the list. The lead-in still must be a complete sentence.
EXAMPLE 3 — THE PAIRING TRAP
✗ My oldest brother — who lives in Chicago, is visiting next week.
An opening dash needs a closing dash, and an opening comma needs a closing comma. Don't mix them.
✓ My oldest brother — who lives in Chicago — is visiting next week.
✓ My oldest brother, who lives in Chicago, is visiting next week.
Grammar — six rules behind almost every error
SAT grammar errors fall into a small number of categories. Master these six and you'll catch the vast majority of grammar questions on the test.
① Subject-verb agreement
Subjects and verbs must match in number: singular subject takes singular verb, plural subject takes plural verb. The SAT's favorite trick is to put words between the subject and the verb to confuse you about what the actual subject is.
EXAMPLE 1 — DON'T BE FOOLED BY WHAT'S CLOSE TO THE VERB
✗ The box of chocolates are on the table.
The subject is "box" (singular), not "chocolates." Strip out the prepositional phrase ("of chocolates") and the agreement is obvious.
✓ The box of chocolates is on the table.
EXAMPLE 2 — INTERRUPTING PHRASES DON'T CHANGE THE SUBJECT
✗ The students, along with their teacher, was excited.
The subject is "students" (plural). "Along with their teacher" is an interrupting phrase, not part of the subject. Phrases that start with "along with," "as well as," "in addition to," or "together with" don't make a subject plural.
✓ The students, along with their teacher, were excited.
EXAMPLE 3 — INDEFINITE PRONOUNS
✗ Each of the players have received a trophy.
"Each" is always singular, even when followed by "of [plural]." Same for "every," "either," "neither," "everyone," "anyone," "no one."
✓ Each of the players has received a trophy.
Quick tricks for finding the real subject
Cross out prepositional phrases. The subject is almost never inside one.
Cross out interrupting phrases set off by commas. They're modifiers, not subjects.
Watch for inverted sentences: "There are three reasons..." — subject is "reasons" (plural), not "there."
Compound subjects with "and" are plural ("Tom and Lisa are"). With "or," the verb matches the closer subject ("Tom or his sisters are"; "His sisters or Tom is").
② Verb tense
Verb tenses should be consistent across a sentence and paragraph unless the meaning genuinely requires a shift. The SAT tests two main kinds of tense problems: random tense switches (always wrong) and the past perfect (the trickier one).
EXAMPLE 1 — DON'T SWITCH TENSE WITHOUT A REASON
✗ Yesterday I walk to the library and read for two hours.
"Yesterday" makes both actions clearly past. Both verbs need to be past tense.
✓ Yesterday I walked to the library and read for two hours.
EXAMPLE 2 — PAST PERFECT FOR THE EARLIER OF TWO PAST EVENTS
✗ By the time we arrived, the movie started.
Both events are in the past, but the movie starting happened before we arrived. Use past perfect ("had started") for the earlier event.
✓ By the time we arrived, the movie had started.
EXAMPLE 3 — PRESENT TENSE FOR ENDURING TRUTHS
✗ The scientist explained that water boiled at 100 degrees Celsius.
Water boiling at 100°C is a permanent fact, not a one-time event. Even within a past-tense sentence, general truths stay in present tense.
✓ The scientist explained that water boils at 100 degrees Celsius.
③ Misplaced and dangling modifiers
A modifier (a descriptive phrase) must sit next to the word it's modifying. The SAT's favorite version of this rule: a modifying phrase at the start of a sentence must describe the subject of the main clause that follows it.
EXAMPLE 1 — DANGLING MODIFIER
✗Walking down the street, the trees seemed to glow in the autumn light.
Trees aren't walking. The opening phrase needs to describe the subject of the main clause — and the subject is "the trees."
✓Walking down the street, I noticed that the trees seemed to glow in the autumn light.
✓As I walked down the street, the trees seemed to glow in the autumn light.
EXAMPLE 2 — A SECOND DANGLE TO RECOGNIZE THE PATTERN
✗Covered in flour, the cake my grandmother was baking smelled delicious.
The cake isn't covered in flour — Grandma is. The opening phrase needs to describe whoever's covered in flour.
✓Covered in flour, my grandmother baked a cake that smelled delicious.
EXAMPLE 3 — MISPLACED (NOT DANGLING) MODIFIER
✗ The author wrote a book about climbing that became a bestseller.
Did "climbing" become a bestseller, or did "the book"? The modifier sits closer to "climbing" but should describe "book."
✓ The author wrote a book that became a bestseller, about climbing.
✓ The author's book about climbing became a bestseller.
Spotting modifier errors quickly
Whenever a sentence opens with a phrase set off by a comma — especially an "-ing" or "-ed" phrase — immediately ask: "Whatever just got described, is it the subject of the main clause?" If the answer is no, the sentence has a dangling modifier.
④ Pronoun agreement and clarity
Two related rules: a pronoun must (a) agree in number with the noun it refers to, and (b) clearly refer to one specific noun, not be ambiguous.
EXAMPLE 1 — NUMBER MISMATCH
✗ Each student must bring their textbook to class.
"Each" is singular; "their" is plural. The SAT enforces strict agreement here, even though spoken English often uses "their" in this context.
✓ Each student must bring his or her textbook to class.
✓All students must bring their textbooks to class.
EXAMPLE 2 — AMBIGUOUS REFERENCE
✗ When Maria visited her grandmother, she was wearing a red sweater.
Who was wearing the sweater — Maria or her grandmother? The pronoun "she" could refer to either.
✓ When Maria visited her grandmother, Maria was wearing a red sweater.
EXAMPLE 3 — COLLECTIVE NOUNS
✗ The committee announced their decision yesterday.
"Committee" is a collective noun acting as one unit — singular. The pronoun should be "its."
✓ The committee announced its decision yesterday.
⑤ Parallel structure
When you list, compare, or pair items in a sentence, every item must be in the same grammatical form. The SAT loves this rule because errors are easy to spot once you know what to look for.
EXAMPLE 1 — IN A LIST
✗ Maya enjoys swimming, hiking, and to bike.
Two gerunds (-ing forms) and one infinitive (to + verb). Match them up.
✓ Maya enjoys swimming, hiking, and biking.
EXAMPLE 2 — IN A COMPARISON
✗ The cost of living in New York is higher than Boston.
Comparing "the cost of living in New York" to "Boston" — apples to oranges. Compare the costs to each other.
✓ The cost of living in New York is higher than that of Boston.
✓ The cost of living in New York is higher than the cost of living in Boston.
EXAMPLE 3 — IN A CORRELATIVE PAIR
✗ The job requires not only technical skill but also being a strong communicator.
"Not only X but also Y" — X and Y must match. "Technical skill" is a noun; "being a strong communicator" is a phrase. Make them parallel.
✓ The job requires not only technical skill but also strong communication.
⑥ Apostrophes
Apostrophes do two things: show possession ("Sara's book") and form contractions ("it's = it is"). They never make plurals. The SAT tests apostrophes mostly through the same handful of frequently-confused word pairs.
its / it's
its = belongs to it it's = it is / it has
their / they're / there
their = belongs to them they're = they are there = location or "there is"
whose / who's
whose = belongs to whom who's = who is / who has
EXAMPLE 1 — ITS vs IT'S
✗ The dog wagged it's tail.
"It's" means "it is" — that doesn't fit here. The tail belongs to the dog, so use the possessive "its" (no apostrophe).
✓ The dog wagged its tail.
EXAMPLE 2 — SINGULAR vs PLURAL POSSESSIVE
Singular possessive: the student's books (one student)
Plural possessive: the students' books (multiple students)
Plural (no possession): the students arrived (no apostrophe)
EXAMPLE 3 — APOSTROPHES NEVER MAKE PLURALS
✗ The store sold three CD's.
There's no possession here — just multiple CDs. No apostrophe.
✓ The store sold three CDs.
Quick decision reference
When you're stuck on a punctuation question, run through this small set of checks before guessing:
If you need to...
Use this
Required structure
Join two complete sentences
Period, semicolon, or comma+FANBOYS
Both sides complete
Add a dependent clause to a main clause
Comma (if dependent comes first)
"Although X, Y."
Introduce a list or explanation
Colon or dash
Lead-in must be a complete sentence
Insert non-essential info
Pair of commas or pair of dashes
Both ends matched (don't mix)
List three or more items
Commas between each
No comma after the last
Show possession
Apostrophe + s (or just apostrophe for plural)
Never for plurals or for "its"
The "complete sentence" test
Almost every punctuation rule on the SAT depends on whether one or both sides of a punctuation mark are complete sentences. Train yourself to ask, every time:
Is what comes before the mark a complete sentence?
Is what comes after the mark a complete sentence?
A complete sentence has a subject and a verb and expresses a complete thought. "Walking to school" isn't complete (no subject + active verb). "She walked to school" is. Once you know which sides are complete, the right punctuation almost picks itself.
Common error — adding extra commas
When in doubt, take a comma out. The SAT often offers options that add unnecessary commas — especially around the subject, between a verb and its object, or before "because." If you can't justify the comma with one of the five rules above, it probably shouldn't be there.