Grammar Rules for Writing

Why This Matters

The PSAT Writing and Language section isn't testing whether you "sound right"—it's testing whether you can identify specific grammatical patterns and fix them efficiently. Every question falls into predictable categories: agreement errors, punctuation boundaries, sentence structure, and word choice. When you understand the underlying rules, you stop guessing based on what "feels" correct and start recognizing exactly what the test is asking.

Here's the key insight: the PSAT recycles the same error types over and over. Subject-verb agreement, pronoun clarity, and punctuation between clauses appear on virtually every test. Don't just memorize that "subjects and verbs must agree"—know how the test hides disagreement (with prepositional phrases, inverted sentences, or tricky indefinite pronouns). That's what separates a good score from a great one.

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Agreement Rules

Agreement errors are the bread and butter of PSAT grammar questions. The core principle: words that refer to each other must match in number, and sometimes in gender or person. The test loves to separate subjects from verbs or pronouns from antecedents to trick your ear.

Subject-Verb Agreement

• Singular subjects take singular verbs; plural subjects take plural verbs—sounds simple, but the PSAT buries the subject under prepositional phrases like "The collection of rare books is valuable"
• Collective nouns (team, committee, group) are typically singular when acting as one unit—"The jury has reached a verdict"
• Indefinite pronouns like everyone, each, nobody, and anyone are always singular—memorize these because they appear constantly

Pronoun-Antecedent Agreement

• Pronouns must match their antecedents in number—"Each student must bring their book" is technically incorrect on the PSAT; the test prefers "his or her" or a rewritten sentence
• Ambiguous pronoun reference is a major trap—if "it" or "they" could refer to multiple nouns, the sentence needs revision
• Place pronouns close to antecedents for clarity—distance creates confusion and signals an error

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Sentence Boundaries and Punctuation

Punctuation questions test one fundamental skill: do you know where one idea ends and another begins? The PSAT wants you to recognize independent clauses (complete sentences) and dependent clauses (fragments that need support), then punctuate accordingly.

Comma Usage

• Use commas after introductory elements—"After the storm, we surveyed the damage" requires that comma; skipping it is an error
• Non-essential information gets commas on both sides—"My brother, who lives in Texas, visited last week" versus "My brother who lives in Texas visited" (no commas if essential)
• Never join two independent clauses with just a comma—this creates a comma splice, one of the most frequently tested errors

Semicolon and Colon Usage

• Semicolons connect two independent clauses without a conjunction—both sides must be complete sentences; "I studied hard; I passed the exam"
• Colons introduce lists, explanations, or elaborations—but the clause before the colon must be a complete sentence
• Semicolons can separate complex list items—especially when items already contain commas, like "Paris, France; London, England; and Tokyo, Japan"

Sentence Fragments and Run-Ons

• Fragments lack a subject, verb, or complete thought—"Because she was tired" is a fragment; it needs an independent clause to complete it
• Run-on sentences jam independent clauses together without proper punctuation—fix with a period, semicolon, or comma + conjunction
• The PSAT often disguises fragments as long phrases—length doesn't equal completeness; check for subject + verb + complete thought

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Verb and Tense Logic

Tense questions test whether you understand when actions happen and whether the timeline stays consistent. The rule: don't shift tenses unless the meaning requires it.

Verb Tense Consistency

• Maintain the same tense within a sentence or passage unless time shifts—"She walked to the store and buys milk" incorrectly mixes past and present
• Past tense for completed actions, present for ongoing or habitual—context clues like "yesterday" or "every day" signal which tense is correct
• Past perfect (had + past participle) shows an action completed before another past action—"She had finished before he arrived"

Active vs. Passive Voice

• Active voice places the subject as the doer—"The scientist conducted the experiment" is clearer and more direct
• Passive voice obscures who performed the action—"The experiment was conducted" removes the actor; the PSAT often flags this as wordy or unclear
• Passive isn't always wrong—use it when the receiver of the action matters more than the doer, but prefer active in most cases

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Sentence Structure and Clarity

These rules ensure sentences are logically constructed and unambiguous. The PSAT tests whether you can spot structural problems that confuse meaning, even when sentences are grammatically "complete."

Parallel Structure

• Items in a list or series must use the same grammatical form—"She likes hiking, swimming, and to bike" breaks parallelism; correct to "hiking, swimming, and biking"
• Parallelism applies to phrases and clauses too—"The coach told them to work hard, stay focused, and that they should rest" mixes infinitives and a clause
• Look for parallel structure in comparisons—"Running a marathon is harder than to sprint" should be "harder than sprinting"

Modifier Placement

• Modifiers must sit next to what they modify—"Covered in chocolate, I ate the strawberries" suggests you are covered in chocolate
• Misplaced modifiers create unintended meanings—"She almost drove her car for six hours" vs. "She drove her car for almost six hours" mean different things
• Dangling modifiers occur when the intended subject is missing entirely—"Walking to school, the rain started" (who was walking?)

Dangling and Misplaced Modifiers

• A dangling modifier has no logical subject in the sentence—"Having finished the assignment, the TV was turned on" implies the TV finished the assignment
• Fix by adding the correct subject—"Having finished the assignment, she turned on the TV"
• These errors often appear at the beginning of sentences—when you see an introductory phrase, check that the subject immediately following is the one performing that action

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Word Choice and Conventions

The PSAT tests whether you know the precise meaning of similar-sounding words and whether you use standard English conventions correctly.

Commonly Confused Words

• Their/there/they're—possessive, location, and contraction of "they are"; the PSAT tests these relentlessly
• Its/it's—possessive pronoun vs. contraction of "it is"; remember that possessive pronouns never use apostrophes (his, hers, its, theirs)
• Effect/affect—effect is usually a noun (the effect), affect is usually a verb (to affect something); memorize the exceptions

Apostrophe Usage

• Apostrophes show possession—singular nouns add 's (the dog's bone), plural nouns ending in s add only an apostrophe (the dogs' bones)
• Contractions use apostrophes to mark missing letters—can't, won't, it's, they're
• Plural nouns never need apostrophes—"The Smith's are here" is wrong; "The Smiths are here" is correct

Comparative and Superlative Adjectives

• Comparatives compare two items and typically end in -er or use "more"—taller, more interesting
• Superlatives compare three or more and end in -est or use "most"—tallest, most interesting
• Irregular forms must be memorized—good/better/best, bad/worse/worst, far/farther/farthest

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Connecting Ideas

Conjunctions and transitions control how ideas relate to each other. The PSAT tests whether you can identify logical relationships and choose the right connector.

Coordinating and Subordinating Conjunctions

• FANBOYS (for, and, nor, but, or, yet, so) join independent clauses of equal weight—use a comma before them when connecting two complete sentences
• Subordinating conjunctions (because, although, since, when, if) create dependent clauses that cannot stand alone
• The relationship must be logical—"She studied hard, so she failed" creates an illogical cause-effect; "but" or "yet" would make sense

Idiomatic Expressions and Prepositions

• Certain verbs pair with specific prepositions—"different from" (not "different than"), "consist of" (not "consist in")
• Idiomatic expressions must be memorized—there's no rule for why we say "interested in" rather than "interested at"
• Preposition errors often sound wrong to native speakers—trust your ear, but verify by checking if the standard phrase matches

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Quick Reference Table

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Self-Check Questions

1. What do subject-verb agreement and pronoun-antecedent agreement have in common, and how do their typical error patterns differ on the PSAT?

2. You see a sentence with a comma between two clauses. What two things must you check to determine if it's a comma splice?

3. Compare misplaced and dangling modifiers: which one has a subject somewhere in the sentence, and which one is missing the subject entirely?

4. A question asks you to choose between "better" and "best." What information in the sentence determines the correct answer?

5. If an FRQ-style question asks you to combine two sentences, what three punctuation options could correctly join two independent clauses?