SAT Grammar Rules: Complete Guide to Standard English Conventions

This page covers 37 essential SAT grammar and punctuation rules across eight categories: commas, other punctuation, verb agreement, pronoun usage, modifier placement, verb tense, sentence structure, and transitions. These rules reflect the Standard English Conventions tested in the SAT Reading and Writing section, including the digital SAT. The SAT does not test memorization of isolated rules — it tests your ability to apply these conventions in context. Each rule includes an explanation and an SAT test-taking tip.

SAT Comma Rules

Unnecessary commas to avoid

Do not place a comma between a subject and its verb, between a verb and its object, or before “that” in a noun clause. These break the natural flow of the sentence and are consistently marked wrong in SAT answer explanations.

SAT Tip: If you can remove the comma without changing the meaning and the sentence reads naturally, the comma is wrong. A long subject phrase does not earn a comma just because it looks like a pause — never separate a subject from its verb with a single comma.

Commas after introductory elements

Use a comma after an introductory word, phrase, or clause that comes before the main clause. This includes prepositional phrases, participial phrases, adverbial clauses, and transitional words.

SAT Tip: Spot the trigger: if the sentence opens with After, When, Although, Because, While, or a similar subordinating conjunction, a comma is expected before the main clause begins.

Commas with non-essential (non-restrictive) clauses

Use commas to set off a clause or phrase that adds extra information but is not essential to identifying the noun. If you can remove it and the sentence still makes sense, it needs commas.

SAT Tip: Try the removal test — cross out the clause. If the sentence still makes clear sense and refers to the same noun, the clause is non-essential and needs commas on both sides.

No comma with essential (restrictive) clauses

Do not use commas around a clause that is essential to identifying which person or thing is being discussed. Removing it would change or lose the meaning of the sentence.

SAT Tip: In SAT-style editing questions, restrictive clauses are typically written with “that” (no commas) and non-restrictive clauses are typically written with “which” (with commas).

Commas with independent clauses (FANBOYS)

Use a comma before a coordinating conjunction (for, and, nor, but, or, yet, so) only when it joins two independent clauses — each of which could stand alone as a complete sentence.

SAT Tip: Check both sides of the conjunction. Does each side have its own subject and verb? If the second part has no subject, no comma belongs before the conjunction.

Commas in a series (Oxford comma)

Use commas to separate three or more items in a series. The SAT uses the Oxford comma — a comma before the final “and” or “or” — in its own passages and answer choices, but does not directly test it as an isolated rule. You won’t see a question where the only difference between choices is the Oxford comma.

SAT Tip: The SAT writes its lists with the Oxford comma, so that’s the form you’ll see in correct answer choices. You don’t need to memorize it as a rule — just recognize it as standard SAT style.

Commas with coordinate adjectives

Use a comma between two adjectives that independently and equally modify the same noun. Test: if you can insert “and” between them or reverse their order naturally, use a comma.

SAT Tip: Try the “and” test: “a long and difficult exam” sounds fine → use a comma. “A red and brick building” sounds odd → no comma needed.

Commas with appositives

An appositive is a noun phrase that renames or describes the noun directly beside it. Non-essential appositives are set off by commas. Essential appositives are not.

SAT Tip: If the appositive just adds extra information about a noun that’s already clearly identified, set it off with commas. Apply the same removal test you’d use for a non-essential clause.

Commas with transitional words and phrases

Transitional words and phrases (however, therefore, for example, in fact) are often set off by commas, but the punctuation must match the sentence structure.

SAT Tip: After a semicolon, a transitional word still needs a comma after it — the pattern is [independent clause]; [transition], [independent clause]. “However” is not a conjunction and can’t join two clauses alone.

SAT Punctuation Rules

Semicolons join independent clauses

A semicolon can replace a period between two closely related independent clauses. It cannot be used before a dependent clause or a phrase.

SAT Tip: Replace the semicolon with a period and read both sides. If both are complete sentences, the semicolon works. If either side falls apart, it’s wrong.

Semicolons in complex lists

When items in a list already contain commas, use semicolons to separate the items instead of commas. This prevents confusion about where one item ends and the next begins.

SAT Tip: If any item in the list contains an internal comma, switch all list separators to semicolons. The SAT tests this with lists of cities and states, names and titles, or dates and places.

Colons introduce explanations or lists

A colon must be preceded by an independent clause. It introduces a list, explanation, or elaboration. Never place a colon directly after a verb or preposition.

SAT Tip: Cover everything before the colon and read it alone. If it’s not a complete sentence on its own, the colon is wrong.

Dashes set off parenthetical information

A pair of dashes can set off non-essential information mid-sentence. A single dash introduces an explanation or list at the end of a sentence. Dashes must be used in matching pairs when interrupting mid-sentence.

SAT Tip: If a dash opens a parenthetical, a closing dash must close it. Don’t let a comma close what a dash opened — mixed punctuation (dash open, comma close) is a common SAT trap.

A single dash introduces a summary or elaboration

A single dash at the end of an independent clause introduces a restatement, elaboration, or surprise. It should not appear mid-sentence without a matching closing dash.

SAT Tip: A single dash works like a dramatic pause before a payoff. If it appears mid-sentence without a second dash, it is being misused.

Apostrophes: singular possession

To show that a singular noun owns something, add an apostrophe + s. This applies to all singular nouns, including those that already end in s.

SAT Tip: Even singular nouns ending in s (like James or class) take apostrophe + s: James’s notebook, the class’s average.

Apostrophes: plural possession

For plural nouns that already end in s, add only an apostrophe after the s. For irregular plurals that do not end in s, add apostrophe + s.

SAT Tip: Ask: is the noun plural and does it end in s? Just add an apostrophe: students’, teachers’. Irregular plurals (children, men) take ‘s: children’s, men’s.

Apostrophes: its vs. it’s

“It’s” is always a contraction meaning “it is” or “it has.” “Its” is the possessive form of “it” and never takes an apostrophe. This is one of the most frequently tested distinctions on the SAT.

SAT Tip: Substitute “it is” wherever you see “it’s.” If the sentence still makes sense, the apostrophe belongs. If it sounds wrong, use “its” with no apostrophe.

Apostrophes: never use for standard plurals

Apostrophes should not be used to make standard plurals. This includes regular nouns, numbers, acronyms, and decades. Add only an s (or es) to form a plural.

SAT Tip: Decades (1990s), acronyms (CEOs), and regular nouns don’t use apostrophes to form plurals. If you see an apostrophe on a straightforward plural, it’s wrong.

SAT Subject-Verb Agreement Rules

Subject-verb agreement basics

A verb must agree in number with its subject, not with nearby nouns. Singular subjects take singular verbs; plural subjects take plural verbs.

SAT Tip: Cross out any prepositional phrase between the subject and verb to isolate the true subject. “The list of requirements is long” — cross out “of requirements” and the agreement becomes obvious.

Inverted sentences and agreement

When a sentence begins with “there” or “here,” the subject follows the verb. Find the real subject to determine the correct verb form.

SAT Tip: Flip the sentence to standard order: “Three main reasons are there.” Now the subject-verb relationship is obvious and easy to check.

Collective nouns as subjects

In American English, collective nouns like team, committee, group, and jury are usually treated as singular when acting as one unit. They take singular verbs in most SAT contexts.

SAT Tip: In SAT-style editing questions (American English), treat collective nouns as singular unless context strongly suggests otherwise.

Compound subjects with “or” and “nor”

When subjects are joined by “or” or “nor,” the verb agrees with the subject closest to it.

SAT Tip: Cover everything before the final subject. What’s the noun closest to the verb? That noun controls agreement — “Neither the students nor the teacher was prepared.”

Indefinite pronouns as subjects

Indefinite pronouns such as each, every, either, neither, one, anyone, everyone, nobody, and someone are always singular and take singular verbs.

SAT Tip: Memorize the always-singular list: each, every, either, neither, one, anyone, everyone, someone, nobody, no one. When you see one of these as the subject, the verb is singular — regardless of what follows.

SAT Pronoun Rules

Pronoun-antecedent agreement

A pronoun must agree in number with the noun it refers to (its antecedent). On SAT questions, choose the option that is grammatically consistent and clearest in context. Watch for pronouns that clearly fail to match a noun in number or create ambiguity.

SAT Tip: The clearest fix for a number-agreement problem is often to make the antecedent plural so “their” works naturally. “All students must submit their own work” is unambiguous and grammatically clean.

Pronoun case: subject vs. object

Use subject pronouns (I, he, she, we, they) when the pronoun is the subject of a verb. Use object pronouns (me, him, her, us, them) when the pronoun is an object of a verb or preposition.

SAT Tip: Remove the other person and test alone: you’d never say “between I” or “gave I the award.” Prepositions (between, for, with) always take object pronouns.

Avoiding shifts in person

Stay consistent in your use of first, second, and third person within a sentence or passage. Shifting from “one” or “a person” to “you” mid-sentence is a common SAT error.

SAT Tip: In SAT-style editing questions, “you” or “your” inserted into an otherwise third-person passage is nearly always the wrong answer. Scan the surrounding sentences to confirm the passage’s person before choosing.

SAT Modifier Placement Rules

Introductory modifiers must modify the subject

A participial or descriptive phrase at the start of a sentence must logically modify the subject of the main clause — the first noun after the comma.

SAT Tip: Ask: who or what is performing the action in the opening phrase? That person or thing must be the grammatical subject of the main clause. If it isn’t, it’s a dangling modifier.

Misplaced modifiers

A modifier should be placed as close as possible to the word it modifies. When a modifier is too far from its target, it creates unintended meaning. Moving the modifier next to the word it describes usually fixes the problem.

SAT Tip: Ask what the modifier is logically describing in each answer choice. The correct placement produces one clear, unambiguous meaning.

That vs. which

In SAT-style editing questions, restrictive (essential) clauses are typically written with “that” and no commas. Non-restrictive (non-essential) clauses are typically written with “which” and commas.

SAT Tip: “That” limits — it identifies which one. “Which” adds — it gives extra info. If the clause is essential to meaning, use “that” with no commas. If it’s extra information, use “which” with commas.

SAT Verb Tense Rules

Consistency of tense within a passage

Tense should remain consistent throughout a passage unless there is a clear logical reason for a shift. Randomly switching between past and present tense is an error.

SAT Tip: SAT questions often include a verb with incorrect tense inside a sentence that is otherwise consistent. Read two sentences before and after the question — the surrounding tense tells you what to match.

Simple past vs. past perfect

Use simple past for a completed action. Use past perfect (had + past participle) when you need to clarify that one past action was completed before another past action.

SAT Tip: Words like “by the time,” “before,” and “after” can signal that one event preceded another — your cue to consider past perfect (had + verb). But check the context: when the sequence is already clear, simple past can also be correct.

Conditionals: real vs. hypothetical

In conditional sentences, tense pairings must be logical. Real/possible conditions use present + future. In present unreal conditionals, the if-clause typically uses a past-tense form and the result clause uses would + base verb. Never use “would” in the “if” clause.

SAT Tip: Spot “would” in the if-clause and eliminate that choice immediately. “If she would study” is always wrong — the if-clause takes a past-tense form, not “would.”

SAT Sentence Structure Rules

Avoiding run-on sentences

A run-on sentence joins two independent clauses without proper punctuation or a conjunction. Fix with a period, semicolon, comma + coordinating conjunction, or a subordinating conjunction.

SAT Tip: Find both subjects and both verbs. If two complete thoughts are fused with no punctuation or conjunction between them, it’s a run-on. Any answer that fixes the boundary without creating a fragment is a candidate.

Avoiding sentence fragments

A sentence must have a subject and a predicate and express a complete thought. A dependent clause or a phrase alone cannot stand as a sentence.

SAT Tip: Subordinating conjunctions (although, because, since, while, if) create dependent clauses that cannot stand alone. If the only verb in a “sentence” is inside a dependent clause, it’s a fragment.

Correlative conjunctions must be parallel

Paired conjunctions — both/and, either/or, neither/nor, not only/but also — must be followed by grammatically parallel structures on each side.

SAT Tip: Whatever grammatical form follows the first conjunction must be mirrored exactly after the second. Cover the first element and check that the second matches its form — “Both [adj] and [adj],” not “Both [adj] and [verb phrase].”

SAT Transition Words Rules

Contrast transitions

Use contrast transitions when the second idea opposes or qualifies the first. Common words: however, although, despite, nevertheless, on the other hand, yet, while.

SAT Tip: Identify the relationship before reading the answer choices. Eliminate any transition that signals agreement or cause-and-effect when the two ideas clearly contrast. “Furthermore” signals addition — not contrast.

Addition and elaboration transitions

Use addition transitions when the second idea supports or extends the first. Common words: furthermore, moreover, in addition, also, similarly.

SAT Tip: Ask: is the second idea surprising, or does it build on the first? Building on = addition (moreover, furthermore). Surprising or opposing = contrast (however, nevertheless).

Cause-and-effect transitions

Use causal transitions when one idea results from or leads to another. Common words: therefore, thus, consequently, as a result, because, since.

SAT Tip: Identify the cause and the effect before choosing. “For example” introduces an illustration, not a result — it’s a common wrong-answer trap when the sentence actually shows a consequence.