SAT Writing and Language: Grammar Rules That Actually Matter

What SAT Writing Actually Tests

The Digital SAT mixes Reading and Writing into one section. Roughly half the questions test grammar, punctuation, and rhetorical choices — what used to be the standalone Writing section.

Good news: the rule list is short and repeats. About 15 rules cover almost every Writing question on every test. Master them and your accuracy climbs fast.

About 15 grammar rules cover the vast majority of SAT Writing questions.

Rule 1: Subject-Verb Agreement

Singular subjects take singular verbs ('the dog runs'); plural subjects take plural verbs ('the dogs run'). Easy in short sentences, tricky when prepositional phrases hide the real subject.

Example: 'The collection of rare books are on display.' Wrong — the subject is 'collection' (singular), so it should be 'is.' Strip out 'of rare books' and you see the agreement instantly.

Mentally remove prepositional phrases (of..., for..., with...) to find the true subject.

Rule 2: Pronoun Clarity and Agreement

Every pronoun must clearly point to one specific noun. 'When Lisa met Sara, she was nervous' — who was nervous? Ambiguous. The SAT wants clear antecedents.

Pronouns must also agree in number. 'Each student must bring their own pencil' — strict SAT grammar prefers 'his or her' for singular antecedents.

Rule 3: Apostrophes — Possession vs Contraction

Apostrophes do two jobs: show possession ('the dog's bone') or contract two words ('it's = it is'). Easy to mix up.

'Its' is possessive (the cat licked its paw). 'It's' is a contraction (it's raining). 'Whose' is possessive; 'who's' is the contraction. The SAT loves to test this distinction.

Writing 'it's' when you mean 'its' (or vice versa). The SAT tests this constantly.

Rule 4: Commas — When and When NOT to Use Them

Use commas to separate items in a list, after introductory phrases, around non-essential information, and before coordinating conjunctions joining two independent clauses.

Do not use commas between a subject and its verb, between two items joined by 'and,' or to splice two independent clauses (that creates a comma splice — major SAT error).

Rule 5: Semicolons — Only Between Independent Clauses

A semicolon joins two independent clauses (each could stand alone as a sentence). 'I love coffee; my brother prefers tea.' Both halves are complete sentences.

If either side is not a complete sentence, you cannot use a semicolon. Try the period test: would each half work as its own sentence with a period?

Semicolon = period strength. If you can't use a period, you can't use a semicolon.

Rule 6: Colons — Introduce a List or Explanation

A colon must follow an independent clause and is used to introduce a list, an explanation, or a single noteworthy item. 'She brought three things: a notebook, a pen, and a lunch.'

Colons cannot follow incomplete sentences. 'She brought: a notebook' is wrong because 'She brought' is incomplete on its own.

Rule 7: Dashes — Use Them Like Commas (But Stronger)

Em-dashes can replace commas to set off non-essential information with extra emphasis. 'The exhibit — featuring rare manuscripts — opens Friday.'

Dashes can also replace a colon for an emphatic interruption. 'There is one ingredient that makes this dish — saffron.' On the SAT, matched dashes (one on each side) are the rule.

Rule 8: Modifier Placement

An opening descriptive phrase must modify the noun that immediately follows. 'Walking through the park, the trees were beautiful' — wrong, the trees were not walking. 'Walking through the park, I saw beautiful trees' — right.

Whenever a sentence opens with an -ing phrase or a participial phrase, ask: 'Who or what is doing this action?' That noun must come right after the comma.

Rule 9: Parallel Structure

When you list items, they must share grammatical form. 'I like running, swimming, and to bike' breaks parallelism. 'Running, swimming, and biking' fixes it.

Watch for lists of three or four items, comparisons using 'than,' and any 'either/or,' 'neither/nor,' or 'not only/but also' construction.

Rule 10: Verb Tense Consistency

Stay in one tense unless there is a clear reason to switch. If the passage is in past tense, do not jump to present mid-sentence.

Past perfect ('had walked') describes an action completed before another past action. Use it when the timing matters: 'By the time we arrived, the show had started.'

Rules 11–15: Transitions, Conciseness, Idioms, Word Choice, Syntax

Rule 11 — Transitions: pick the word that matches the logical relationship (cause, contrast, addition, sequence). Rule 12 — Conciseness: when in doubt, pick the shortest grammatically correct option. Rule 13 — Idioms: certain prepositions go with certain words ('preoccupied with,' not 'preoccupied for').

Rule 14 — Word Choice: pick the most precise word, not the fanciest. Rule 15 — Syntax: keep modifiers near what they modify, keep verbs near their subjects, keep sentences clear.

How to Drill Grammar in 15 Minutes a Day

Pick one rule per day. Spend 5 minutes reading examples, 10 minutes drilling 5–10 questions on that rule, and 2 minutes writing down what you got wrong. In 15 days, you have covered every major rule once.

Then run a second cycle, faster. (Our Writing question banks let you filter by rule type — practice subject-verb agreement on Monday, commas on Tuesday, and so on.)