What this lesson covers
- The complete-thought test (subject + verb + stands alone)
- The legal walls: period, semicolon, comma + FANBOYS — and the illegal lone comma
- Dependent clauses: leading takes a comma, trailing usually doesn’t
- Colons, semicolon fragments, two practice questions, and the three traps
Questions worked in the video
- 0:55The experiment failed, the results were still useful. (fix the splice)
- 1:16Because the storm knocked out power(,) the lab lost a week of data — where does the comma go?
- 2:01Coral reefs support thousands of species ___ they cover less than 1% of the ocean floor.
- 2:30The hikers reached the summit at noon ___ the view stretched for miles.
Chapters
- 0:00The wall that isn’t
- 0:17The complete-thought test
- 0:36The three legal walls
- 0:55Worked: the splice, fixed three ways
- 1:16Worked: dependent clauses
- 1:37Deeper: colons & semicolon fragments
- 2:01Practice 1
- 2:30Practice 2 (comma + however)
- 2:55Three traps
- 3:14Recap
Lesson transcript
The narration of the video, word for word, under its chapter headings.
0:00The wall that isn’t
Welcome to SAT Climb. Commas, semicolons, periods — boundary questions. The SAT's favorite version: two complete thoughts, and a choice about what goes between them. Get the walls right, and these are free points.
0:17The complete-thought test
First, the one skill everything hangs on: spotting a complete thought. A subject, a verb, and it stands alone. The experiment failed — complete. Because the experiment failed — not complete. That word because leaves it hanging. Complete thought, complete wall.
0:36The three legal walls
Here are the legal walls between two complete thoughts. A period. A semicolon — same strength, just quieter. Or a comma plus a FANBOYS word: for, and, nor, but, or, yet, so. And the one illegal wall the SAT loves: a comma by itself. That's the comma splice.
0:55Worked: the splice, fixed three ways
Look at this one. The experiment failed, comma, the results were still useful. Two complete thoughts, one lonely comma — splice. Three legal fixes. Period: failed. The results. Semicolon: failed; the results. Or comma plus but: failed, but the results were still useful. All three work. The comma alone never does.
1:16Worked: dependent clauses
Now dependent clauses. Because the storm knocked out power, comma, the lab lost a week of data. When the dependent clause leads, it takes a comma. Flip it — the lab lost a week of data because the storm knocked out power — and the comma disappears. Leading clause, comma. Trailing clause, usually none.
1:37Deeper: colons & semicolon fragments
The deeper cases. A colon introduces a list or an explanation — but only after a complete thought. The recipe calls for three ingredients: flour, water, salt. Cut it short — the recipe calls for, colon — and the colon breaks. Same rule for semicolons: both sides must stand alone. A semicolon followed by a fragment is always wrong.
2:01Practice 1
Your turn. Coral reefs support thousands of species, blank, they cover less than one percent of the ocean floor. Find the complete thoughts, then build the wall. Pause if you need more time. Two complete thoughts, and the logic is contrast. Comma plus yet — a legal wall with the right meaning. The bare comma is a splice. Nothing at all is a run-on.
2:30Practice 2 (comma + however)
One more. The hikers reached the summit at noon, blank, the view stretched for miles. Careful — one of these walls only looks legal. Pause if you need it. However is not one of the FANBOYS — a comma plus however is still a splice. Both sides stand alone, so you need the semicolon. B.
2:55Three traps
Three traps. Trusting a comma to hold two complete thoughts — it can't; that's the splice. Adding a comma before every and — you only need it when a complete thought follows. And putting a semicolon in front of a fragment — semicolons demand complete thoughts on both sides.
3:14Recap
Boundaries: solved. Find the complete thoughts, then build a legal wall. Start free at satclimb.com.
Read the written version: the Boundaries (Punctuation) strategy guide, then try 25 hard Boundaries (Punctuation) questions with full explanations. Both are free, no account needed.