Boundaries
Sentence boundaries tell you where one clause ends and the next begins, and SAT questions test whether you should mark that boundary or leave it alone.
核心知识
Sentence boundaries are the points where one grammatical unit ends and another begins. The SAT tests whether you can mark these boundaries with the right punctuation—or recognize when no punctuation is needed at all.
深入理解
Every sentence is built from clauses—groups of words with a subject and a verb. Some clauses can stand alone (independent clauses), and some can't (dependent clauses). The punctuation between and around these clauses is what the SAT calls "boundaries."
Think of punctuation as traffic signals for readers. A period is a red light: full stop. A semicolon is a yellow light: slow down, related idea ahead. A comma with a conjunction is a gentle merge. Getting these signals wrong—or leaving them out—creates confusion.
The core skill: identify whether you're looking at one clause or two, whether each clause is independent or dependent, and then apply the punctuation rules that match.
Most boundary questions follow a pattern:
- Read the full sentence to find the clauses.
- Determine which clauses are independent and which are dependent.
- Check what punctuation the answer choices offer.
- Eliminate choices that create fragments, run-ons, comma splices, or misuse punctuation marks.
This topic covers nine specific boundary skills, from basic comma splice recognition to subtle judgment calls about colons, dashes, and ambiguous boundaries.
知识点教程
9Identify and fix sentence fragments, run-ons, and comma splices.
Recognize fragments, run-ons, and comma splices, then choose the boundary that makes the sentence co
Punctuate boundaries between independent clauses (period, semicolon, comma+conjunction).
Two independent clauses can be separated by a period, semicolon, or comma plus coordinating conjunct
Use semicolons with conjunctive adverbs (e.g., however, therefore) when appropriate.
Join independent clauses with a semicolon before conjunctive adverbs like however or therefore.
Use commas to separate introductory/dependent elements from independent clauses when needed.
Put a comma after an introductory dependent clause or phrase before the main clause.
Use commas to set off nonessential clauses/phrases/appositives.
Set off nonessential information with commas, and leave essential information unpunctuated.
Use colons to introduce elaborations (lists, explanations) when grammatically valid.
Use a colon only after a complete clause to introduce a list, explanation, or elaboration.
Use dashes or parentheses to set off parenthetical information when appropriate.
Use matching dashes or parentheses to set off extra parenthetical information.
Eliminate unnecessary punctuation that breaks subject–verb or other tight relationships.
Do not break tight grammatical pairs like subject-verb or verb-object with stray punctuation.
Choose punctuation that makes subtle sentence boundaries unambiguous.
Use punctuation to remove ambiguity when a phrase could attach in more than one way.