Standard English Conventions: The Complete Grammar Rulebook

Sentence boundaries

A complete sentence needs at least one independent clause: a subject and a verb that express a complete thought. Two independent clauses cannot be joined with just a comma — that's a comma splice — and they cannot be left as two separate sentences with no connector if the question is asking you to combine them correctly. The four correct ways to join two independent clauses are a period, a semicolon, a comma plus a coordinating conjunction (for, and, nor, but, or, yet, so), or a comma after an introductory dependent clause.

The most reliable way to check a sentence boundary question is to isolate each clause and ask whether it could stand alone as a complete sentence. If both clauses are independent, you need one of the four correct joining methods. If one clause is dependent (it starts with a word like 'because,' 'although,' or 'since' and can't stand alone), a comma alone is often correct.

Subject-verb and pronoun-antecedent agreement

Subjects and verbs must agree in number: singular subjects take singular verbs, plural subjects take plural verbs. The trap on the SAT is almost always a long phrase between the subject and verb that makes the subject harder to identify — cross out prepositional phrases and other interrupters to find the true subject before checking the verb.

Pronouns must agree in number and, where relevant, gender with their antecedent — the noun they refer to. Watch for collective nouns like 'team' or 'company,' which are typically treated as singular in American English, and for indefinite pronouns like 'each' or 'everyone,' which are also singular even though they can feel like they refer to multiple people.

Verb tense, mood, and form

Verb tense questions test whether the tense used is consistent with the timeline established elsewhere in the sentence or passage. Look for time-marker words and phrases such as 'yesterday,' 'by next year,' 'has already,' or 'since 2020' — these anchor the correct tense. A sentence that shifts tense without a logical reason for the shift is incorrect.

You'll also see questions on verb form, including matching a main verb to an auxiliary verb correctly (has gone vs. has went) and choosing between similar forms like the past participle and the simple past. When in doubt, identify the full verb phrase, including any helping verbs, before deciding whether the main verb's form is correct.

Punctuation

Commas, semicolons, colons, dashes, and apostrophes each have specific, testable jobs. A common failure mode is treating a dash and a comma as interchangeable for a nonessential clause — they can be, but only when used in matching pairs; mixing a comma and a dash around the same clause is incorrect. Colons and dashes can also introduce a list or explanation, but only after a complete independent clause.

Apostrophe questions test possession, not plurals — 'the dog's leash' shows one dog possessing a leash, while 'the dogs' leashes' shows multiple dogs each with a leash. 'Its' (no apostrophe) is possessive, while 'it's' (with apostrophe) is a contraction for 'it is.' This distinction is tested frequently enough that it's worth automating.

Modifiers

A modifier should be placed as close as possible to the word it describes. A misplaced or dangling modifier occurs when the word or phrase being modified is missing from the sentence or is placed too far from the modifier, creating an unintended meaning. Classic dangling modifiers show up as introductory phrases: 'Running late for class, the bus was missed by Maria' illogically implies the bus was running late, since 'the bus' immediately follows the modifier.

To check a modifier question, identify the modifying phrase, then ask what noun immediately follows it (for introductory modifiers) or what noun it sits next to (for other modifiers). If that noun isn't logically the thing being described, the sentence needs to be restructured so the correct noun follows the modifier.

Parallel structure

When a sentence presents a list or a series of comparable items, each item must share the same grammatical form. A sentence that reads 'She enjoys hiking, to swim, and reading' breaks parallelism because 'to swim' doesn't match the -ing form of the other two items. This rule also applies to paired constructions like 'not only...but also' and 'either...or,' where the phrase following each half of the pair should match structurally.

The fastest way to check parallel structure is to isolate the list or paired items and read them independently of the rest of the sentence, checking that each one is the same part of speech and verb form as the others.

Worked example: sentence boundaries

Worked example: agreement

Worked example: punctuation