Form, structure, and sense: modifiers, plurals and possessives
1 h 10 min of study
This unit is ≈13% of the SAT, across 5 lessons. Full syllabus
Lesson 1 of 5 · Standard English conventions
Boundaries: linking clauses and sentences
8 min read · about 1 h 50 min with practice3 quick checks≈4% of the testCore: Core: tested on most papers
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Boundaries questions test where one sentence ends and the next begins, and how two clauses may legally be joined. They appear several times in every module among the other Standard English Conventions items. The rules are few and fixed, so a 1550 scorer gets essentially every one right in 30–45 seconds.
By the end you’ll be able to
Correctly join or separate independent clauses with periods, semicolons, colons, dashes, and a comma plus a coordinating conjunction
Recognize and fix run-on sentences, comma splices and fragments
Punctuate conjunctive adverbs and transitional phrases (however, therefore, in fact) correctly between and within clauses
Use colons and dashes to introduce explanations, lists and elaborations after a complete clause
What the exam asks
Stem: “Which choice completes the text so that it conforms to the conventions of Standard English?”
Choices differ only in punctuation, sometimes with a small change in form (which vs. it, helped vs. helping).
What is tested: joining or separating independent clauses, comma splices, run-ons, fragments, conjunctive adverbs (however, therefore), colons and dashes after a complete clause, and the period at the end of an indirect question.
Position: after Information and Ideas, ordered by difficulty rather than by skill.
Core ideas
Step zero: find the independent clauses
An independent clause (IC) has a subject and a finite (tense-carrying) verb and could stand alone as a sentence. These are not independent clauses:
A clause that begins with a subordinator: because, although, while, when, if, since, unless, whereas, after, before.
A relative clause: which..., who..., where...
A phrase with no finite verb: leaving gaps..., by damming streams, a slab of stone inscribed with...
Test each side of the blank by asking, “Could this stand alone as a sentence?”
Joining two independent clauses
Pattern
Example
Verdict
IC. IC
The storm ended. Crews began repairs.
✔
IC; IC
The storm ended; crews began repairs.
✔
IC, FANBOYS IC
The storm ended, and crews began repairs.
✔ (for, and, nor, but, or, yet, so)
IC: IC
The cause was clear: the dam had cracked.
✔ when the second clause explains or illustrates the first
IC—IC
The cause was clear—the dam had cracked.
✔ (a single dash works like a colon)
vii.Check your understanding
3 questions on boundaries: linking clauses and sentences. Every option is explained once you answer.
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PromptCard 1 of 3
What makes a clause independent?
IC, IC
The storm ended, crews began repairs.
✘ comma splice
IC IC
The storm ended crews began repairs.
✘ run-on
IC FANBOYS, IC
The storm ended and, crews began repairs.
✘ comma on the wrong side of the conjunction
Attaching something that is not an independent clause
Pattern
Example
Verdict
DC, IC
Because the storm ended, crews began repairs.
✔
IC, which...
The storm ended, which let crews begin repairs.
✔
IC, -ing phrase
The storm ended, allowing crews to begin repairs.
✔
IC; DC or IC; phrase
The storm ended; which let crews begin repairs.
✘ a semicolon needs an IC on both sides
DC. IC
Because the storm ended. Crews began repairs.
✘ fragment
A semicolon is a period
Wherever a semicolon is correct, a period is also correct, and the reverse is true too. Two consequences follow:
To test a semicolon, replace it with a period and ask whether both halves are complete sentences.
If two choices are identical except that one has “; “ and the other “. “, both are wrong, because the SAT never keys two answers.
Colons and dashes
Before a colon you need a complete independent clause. Never put a colon after such as, including or a bare verb (The colors are: red...).
After a colon can come anything that explains, lists or illustrates what came before, whether or not it is a complete clause.
A single dash behaves like a colon. A pair of dashes behaves like a pair of commas, so if a dash opens an interruption, the blank often needs its partner.
Conjunctive adverbs are not conjunctions
However, therefore, thus, consequently, moreover, nevertheless, instead, meanwhile, in fact, for example and as a result cannot join two independent clauses with only a comma.
Where the adverb sits
Correct punctuation
At the start of the second IC
IC**; however,** IC or IC**. However,** IC
Interrupting one clause
The sample**, however,** was small.
At the end of the first IC
The sample was small**, however;** the results were striking.
Logic decides the hard items. Sometimes both “X; however, Y” and “X, however; Y” are punctuated legally. Then ask which clause actually contrasts with what came before. The adverb belongs in that clause.
Fragments hiding behind long subjects
Every sentence needs a subject and a finite verb. Hard items bury the subject under a long appositive or a noun clause:
The Antikythera mechanism, a bronze device recovered from a Roman-era shipwreck in 1901,modeled the motions of the Sun and Moon. There is no boundary before modeled.
What surprised the researchers mostwas the colony’s age. A noun clause is the subject, so no punctuation goes before the verb.
Indirect questions
An indirect question is a statement and ends with a period: Linguists have asked why the language lacks number words. Use a question mark only for a direct question.
Worked examples
Exam technique
Look at the choices first. Punctuation-only differences signal a Boundaries item.
Read the whole sentence, plus the one before it if a conjunctive adverb appears.
Label both sides of the blank: independent clause or not?
Apply the tables. Eliminate “twins” (identical period and semicolon choices), splices and colons after incomplete clauses.
For adverbs, work in two steps. First find the boundary. Then place the adverb in the clause it logically belongs to.
Pace: 30–45 seconds. Time saved here funds the harder Inferences and Command of Evidence items.
Common mistakes
Quick recap
Identify each side of the blank as an independent clause or not before you look at punctuation.
Two independent clauses: use a period, a semicolon, a comma + FANBOYS, or a colon or dash when the second explains the first.
A comma alone between two independent clauses is a splice, and no punctuation at all is a run-on.
A semicolon equals a period, and both need complete clauses on each side.
Colons need a complete clause before them. What follows can be a list, a phrase or a clause.
Conjunctive adverbs take “; however,” between clauses and “, however,” inside a clause. Logic decides placement.
Long subjects still need their verb, and indirect questions end with a period.