Free lesson · Reading & Writing · Boundaries
Six marks, one decision.
About one in eight Reading & Writing questions comes down to a single punctuation mark. In five short steps you will learn what each mark requires, practice spotting it, and prove it on a 6-question quiz.
Grab paper. Taking notes is part of the lesson.
Step 1 of 5 · 4 min
Every boundary mark has one job
Each punctuation mark on the SAT is tested by what it requires on each side. Flip through the six cards. For each one, read the single rule, then watch it solve a real SAT-style question step by step.
Write each mark and its rule in your notes.
Period
Sentence + Sentence. Two complete thoughts, fully separated.
🔑 Test: cover the mark. Is there a full sentence on BOTH sides? If yes, a period is always legal.
Worked question
Wind turbines now supply a fifth of the region's power ______ planners expect that share to double.
- 1Cover the blank. Left: "Wind turbines now supply a fifth of the region's power." Full sentence.
- 2Right: "planners expect that share to double." Also a full sentence.
- 3Two full sentences with no joining word need a hard stop. A comma alone is a splice, nothing is a run-on.
Answer: B