Top 15 SAT Grammar Rules You Must Know for 2026
The Digital SAT's Reading and Writing section tests a specific set of grammar rules repeatedly. These are not obscure or advanced grammar concepts — they are the same core rules tested every single test date, just presented in different passages and contexts. Learning these 15 rules and recognizing how they appear on the test is the fastest way to improve your Reading and Writing score.
This guide covers each rule with examples of how it appears on the Digital SAT, the trap answers the College Board uses, and quick strategies for spotting the correct choice. For a broader preparation strategy, see our SAT Reading & Writing Guide.
For a complete overview of the Digital SAT format and scoring, see our SAT Score Chart guide. If you are an international student, our SAT for International Students guide covers the unique challenges non-native English speakers face with grammar on the SAT.
Rule 1: Subject-Verb Agreement
The subject and verb must agree in number: singular subjects take singular verbs, plural subjects take plural verbs.
How the SAT tests it: The College Board places words between the subject and verb to disguise the true subject. A common pattern: 'The collection of rare books [is/are] valuable.' The subject is 'collection' (singular), not 'books,' so the correct verb is 'is.'
Quick strategy: Cross out prepositional phrases and relative clauses between the subject and verb. Identify the actual subject and match it to the verb.
Rule 2: Pronoun-Antecedent Agreement
Pronouns must agree in number and gender with the nouns they replace (their antecedents).
How the SAT tests it: 'When a student submits [their/his or her/its] application, [they/he or she/it] should check for errors.' The College Board tests whether you can match the pronoun to the correct antecedent, especially in sentences with multiple nouns.
Quick strategy: Find the antecedent (the noun the pronoun refers to), check if it is singular or plural, and select the matching pronoun.
Rule 3: Pronoun Clarity (Ambiguous Reference)
A pronoun must clearly refer to one specific noun. If a sentence contains two possible antecedents, the pronoun reference is ambiguous.
How the SAT tests it: 'The manager told the employee that he needed to improve.' Who needs to improve — the manager or the employee? The SAT rewards answers that eliminate ambiguity, often by replacing the pronoun with a specific noun: 'The manager told the employee that the employee needed to improve.'
Rule 4: Comma Splices and Run-On Sentences
Two independent clauses cannot be joined with only a comma (comma splice) or with no punctuation at all (run-on).
Correct ways to join independent clauses: Period. Semicolon. Comma + coordinating conjunction (for, and, nor, but, or, yet, so — FANBOYS). Dash. Colon (when the second clause explains the first).
How the SAT tests it: You are given a sentence with two independent clauses and asked to choose the correct punctuation. The trap answer is always the comma-only option.
Rule 5: Dangling and Misplaced Modifiers
An introductory modifying phrase must describe the noun immediately following it. If the wrong noun follows the modifier, the sentence is grammatically incorrect (and often absurd).
Example: 'Walking through the park, the trees were beautiful.' This says the trees were walking. Correct: 'Walking through the park, I found the trees beautiful.' The modifier 'Walking through the park' must be followed by the person doing the walking.
Quick strategy: When you see a sentence beginning with a participial phrase (an -ing or -ed phrase), immediately check: does the subject after the comma actually perform that action?
Rule 6: Parallel Structure
Items in a list, comparison, or series must be in the same grammatical form.
Wrong: 'She enjoys reading, to swim, and hiking.' Correct: 'She enjoys reading, swimming, and hiking.' All three items must be in the same form (gerunds in this case).
How the SAT tests it: Lists with 3+ items, 'not only ... but also' constructions, and comparisons using 'rather than,' 'more than,' or 'as ... as' structures.
Rule 7: Apostrophe Rules (Possession vs Contraction)
Apostrophes show possession (the dog's bone) or indicate contractions (it's = it is). They are never used to make nouns plural.
Critical distinctions:
- its (possessive) vs it's (it is) — this is tested constantly
- their (possessive), they're (they are), there (location)
- whose (possessive) vs who's (who is)
- your (possessive) vs you're (you are)
Quick strategy: Replace the word with the expanded form. If 'it is' makes sense in the sentence, use 'it's.' If not, use 'its.'
Rule 8: Colon and Semicolon Usage
A colon introduces a list, explanation, or elaboration — but the clause before the colon must be a complete sentence. A semicolon joins two related independent clauses — both sides must be complete sentences.
How the SAT tests it: You are given choices between comma, semicolon, colon, and dash. The key test: Is the material before the punctuation mark a complete sentence? If yes, a colon or semicolon can work. If no, neither can be used.
Rule 9: Verb Tense Consistency
Verb tenses must be consistent within a sentence and paragraph unless there is a clear reason for a tense shift (such as discussing past events that affect the present).
How the SAT tests it: A passage describes events in one tense, and you are asked whether a verb should be past, present, or present perfect. Look at the surrounding context: if the passage is in past tense, a random present tense verb is incorrect unless it describes a general truth.
Rule 10: Who vs Whom
'Who' is a subject pronoun (like he/she). 'Whom' is an object pronoun (like him/her). 'Who' performs the action; 'whom' receives it.
Quick strategy: Replace 'who/whom' with 'he/him.' If 'he' fits, use 'who.' If 'him' fits, use 'whom.' Example: 'The teacher [who/whom] I admire' → 'I admire him' → 'whom.'
Rule 11: Transitions and Logical Connectors
The SAT tests whether you can choose the correct transition word or phrase to connect ideas logically.
Key categories:
- Contrast: however, nevertheless, on the other hand, in contrast, despite this
- Addition: furthermore, moreover, in addition, additionally
- Cause/effect: therefore, consequently, as a result, thus
- Example: for instance, specifically, in particular, for example
- Concession: although, even though, while, granted
How the SAT tests it: You read two sentences and choose the best transition to connect them. The trap is selecting a transition that sounds sophisticated but expresses the wrong logical relationship.
Rule 12: Sentence Fragments
A sentence must have a subject, a verb, and express a complete thought. A dependent clause standing alone is a fragment.
How the SAT tests it: 'Because the experiment yielded unexpected results.' This is a fragment — 'because' makes it a dependent clause. The SAT may test whether to keep 'because' or replace it with 'the' to create a complete sentence.
Rule 13: Comparisons (Than vs Then, Like vs As)
Comparisons must be between equivalent things. 'The population of China is larger than India' is wrong — it compares population to India (a country). Correct: 'The population of China is larger than that of India.'
Also tested: 'than' (comparison) vs 'then' (time sequence), and 'like' (comparing nouns) vs 'as' (comparing clauses).
Rule 14: Wordiness and Redundancy
The SAT rewards concise writing. If two answer choices convey the same meaning but one uses fewer words, the shorter option is usually correct.
Common SAT redundancies: 'true fact' (all facts are true), 'past history' (all history is past), 'each and every' (pick one), 'completely unanimous' (unanimous already means complete agreement), 'end result' (result already implies an end).
Quick strategy: If the shortest answer choice conveys the same complete meaning as the longer options, choose the shortest one.
Rule 15: Rhetorical Synthesis (New for Digital SAT)
This question type is new to the Digital SAT and asks you to synthesize information from bullet points, notes, or short passages into a single effective sentence.
How the SAT tests it: You are given 3-5 bullet points of information and asked which sentence most effectively combines them for a specific purpose (e.g., 'to introduce the topic to a general audience' or 'to emphasize the economic impact'). The correct answer addresses the stated purpose while accurately incorporating the information.
Quick strategy: Read the purpose statement first (it tells you what to emphasize), then eliminate answers that are inaccurate, incomplete, or do not match the stated purpose.
Frequently Asked Questions
How many grammar questions are on the Digital SAT?
The Reading and Writing section contains 54 total questions, of which approximately 11-15 are Standard English Conventions questions (grammar and punctuation) and 8-12 are Expression of Ideas questions (transitions, wordiness, rhetorical synthesis). The remaining questions test reading comprehension. For a full section breakdown, see our Complete SAT Guide.
Should I study grammar or reading comprehension first?
Grammar rules are the fastest way to improve your Reading and Writing score because they are consistent and learnable — once you know the 15 rules, you can apply them to any question. Reading comprehension improvement takes longer because it requires building vocabulary and reading speed over time. Start with grammar for quick wins, then shift to reading comprehension for sustained improvement. For the full context on how the Reading and Writing section works, see our What Is the SAT guide.
Practice SAT grammar with WitPrep's SAT Reading & Writing Practice. Targeted exercises on all 15 grammar rules with instant feedback and detailed explanations.
Key Takeaways
- The SAT tests the same 15 core grammar rules repeatedly — learning them is the fastest path to improving your Reading and Writing score
- Subject-verb agreement, comma rules, and modifier placement are the three most frequently tested rules
- For punctuation questions, determine whether the text before the punctuation mark is a complete sentence — this eliminates most wrong answers
- Conciseness is rewarded: when two answer choices mean the same thing, the shorter one is usually correct
- Rhetorical synthesis is a new Digital SAT question type that asks you to combine information for a specific purpose — read the purpose statement before evaluating answers