Quick answer: SAT grammar questions test a short list of rules. Most punctuation questions come down to one test: is each side of the punctuation mark a complete sentence? Most grammar questions come down to matching: the verb with its real subject, the pronoun with its noun, the tense with the timeline, and the modifier with the word it describes.
SAT grammar has a reputation for being picky, but the Digital SAT tests a fairly small set of rules, and it tests them the same way again and again. In the Reading and Writing section, these questions belong to the Standard English Conventions domain, which College Board splits into two skills: boundaries (punctuation between and within sentences) and form, structure, and sense (agreement, verb forms, pronouns, and modifiers).
This guide covers the SAT grammar rules that come up most, with an example of each. The examples are short on purpose. On the real test, each question gives you a sentence or two with a blank and four ways to fill it.
The one test behind most punctuation questions
Before you look at the answer choices, find the independent clauses: groups of words with a subject and a verb that could stand alone as a sentence. Then ask what’s on each side of the blank.
- Complete sentence + complete sentence: you need a period, a semicolon, or a comma plus a conjunction (and, but, or, so, for, nor, yet).
- Complete sentence + anything that explains or lists: a colon can work, but only if what comes before it is a complete sentence.
- Complete sentence + a phrase that isn’t a sentence: usually a comma or no punctuation at all, never a semicolon.
Almost every boundaries question is this test in disguise.
Rule 1: Don’t join two sentences with only a comma
Joining two independent clauses with a comma alone creates a comma splice, and the SAT never accepts it.
The museum extended its hours ___ attendance rose by a third.
A) hours, attendance
B) hours; attendance
C) hours attendance
D) hours, and, attendance
Answer: B. “The museum extended its hours” and “attendance rose by a third” are both complete sentences. A semicolon can join them. Choice A is a comma splice, choice C runs them together, and choice D puts an extra comma after “and.”
Rule 2: A semicolon works like a period
Between two sentences, a semicolon and a period do the same job. So if two answer choices differ only by a semicolon versus a period, they can’t both be right, which means neither is the answer; look for the choice that differs in some other way. Both sides of a semicolon must be complete sentences. A semicolon before a phrase like “including several rare maps” is always wrong.
The one exception is lists: semicolons can separate items in a list when the items already contain commas (“Lima, Peru; Quito, Ecuador; and Bogotá, Colombia”). It’s rare, but it does appear.
Rule 3: A colon needs a complete sentence before it
What follows a colon can be a list, a single word, a phrase, or a full sentence, as long as it explains or expands on what came before. What comes before the colon must be able to stand alone.
The researchers identified the problem ___ the sensor had been installed upside down.
A colon works here: “The researchers identified the problem” is complete, and what follows explains it. A colon after “identified” (“identified: the problem”) would not work, because “The researchers identified” doesn’t stand alone.
Rule 4: Commas with conjunctions and introductory phrases
Use a comma before a coordinating conjunction (and, but, so, yet, or, nor, for) when it joins two complete sentences: “The trail was steep, but the view was worth it.” Leave the comma out when the conjunction joins two verbs that share one subject: “She opened the box and found a letter.”
An introductory phrase or clause usually takes a comma before the main sentence: “After the storm passed, the crew inspected the roof.”
Rule 5: Extra information gets matching punctuation on both sides
A nonessential element, meaning information you could delete without breaking the sentence, needs the same punctuation on both sides: two commas, two dashes, or two parentheses.
The novel ___ which took nine years to write ___ was published last spring.
Both blanks need commas (or both need dashes). Mixing a comma on one side with a dash on the other is always wrong, and so is leaving off the second comma. This is one of the most common traps on the test.
Rule 6: No punctuation between a subject and its verb
The SAT likes to put a long subject in front of a verb and tempt you to break it with a comma.
The collection of letters discovered in the attic ___ dates from the 1890s.
The answer has no punctuation at all: “…discovered in the attic dates from the 1890s.” Don’t separate a subject from its verb, or a verb from its object, with a single comma.
Rule 7: Make the verb agree with its real subject
Cross out the phrases between the subject and the verb, then match the verb to what’s left.
The list of required supplies ___ on the course website.
A) appear
B) appears
C) have appeared
D) are appearing
Answer: B. The subject is “list,” which is singular. “Of required supplies” is a phrase that sits between the subject and the verb, and the plural word “supplies” is the trap. Choices A, C, and D are all plural forms.
Watch for the same trick with phrases like “along with,” “as well as,” and “in addition to”: “The coach, along with her assistants, plans the schedule.”
Rule 8: Pronouns must match their nouns
A pronoun has to agree in number with the noun it replaces, and it has to be clear which noun that is.
- “Each of the companies released its report,” not “their,” because “each” is singular.
- “The scientists published their findings,” because “scientists” is plural.
Also know the possessive forms that the SAT tests most: its (possessive) vs. it’s (it is), their (possessive) vs. they’re (they are) vs. there (a place).
Rule 9: Keep verb tense consistent with the timeline
Look for time clues in the rest of the passage, such as dates, “last year,” “currently,” or the tense of nearby verbs, and choose the tense that fits.
In 1969, the agency ___ its first lunar landing.
“Achieved” is right, because 1969 sets the action in the past. “Has achieved” or “achieves” would break the timeline.
Rule 10: Put the modifier next to what it describes
An introductory phrase describes whatever comes right after the comma.
Having finished the experiment, ___
A) the results were recorded by the students.
B) the students recorded the results.
Answer: B. The students finished the experiment, so “the students” must come right after the comma. In choice A, the sentence says the results finished the experiment, which is a dangling modifier.
How to practice SAT grammar
Learning the rules is the first step. Recognizing them quickly inside a real question is what earns points. A few habits help:
- Read the whole sentence before the choices. Find the subject, the main verb, and the independent clauses first.
- Name the rule before you answer. “This is a comma splice question” or “this is subject-verb agreement.” Naming it keeps you from choosing what simply sounds right.
- Read every explanation, especially for wrong answers. The wrong choices repeat across questions. Once you’ve seen why “hours, attendance” fails, you’ll spot comma splices everywhere.
The boundaries practice set drills Rules 1 through 6, and the form, structure, and sense set drills Rules 7 through 10. Every question there explains all four choices. For how grammar fits into the rest of the section, see the Digital SAT format guide.
Frequently asked questions
What grammar rules are on the SAT?
The SAT tests sentence boundaries (commas, semicolons, colons, dashes, and run-ons) and form, structure, and sense (subject-verb agreement, pronoun agreement, verb tense, plurals and possessives, and modifier placement). These make up the Standard English Conventions domain of the Reading and Writing section.
Are SAT grammar questions the same as SAT writing practice?
Grammar is part of SAT writing, but not all of it. The Reading and Writing section also tests transitions and rhetorical synthesis, which are about logic and purpose rather than grammar rules.
Is a semicolon the same as a period on the SAT?
For joining sentences, yes. Both sides of a semicolon must be complete sentences, just as with a period. The only other use the SAT tests is separating list items that already contain commas.
How do I know when to use a colon on the SAT?
Use a colon only when the part before it is a complete sentence and the part after it explains, lists, or expands on it.
What is the fastest way to improve at SAT grammar?
Learn the rules on this page, then practice one rule at a time, naming the rule before you answer each question and reading the explanation for every choice.