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Comma splices: test each side of the comma

Cover one side of the mark, then the other. If both can stand alone as sentences, a comma alone cannot join them: use a full stop, a semicolon, or a comma with a joining word.

  1. 1.Find the gap where the choices differ. Cover everything to the right of it and read what is left.
  2. 2.Ask whether the left side can stand alone as a sentence. It needs a subject and a verb, and it must not begin with a word such as although or because.
  3. 3.Uncover the right side and cover the left. Ask the same question.
  4. 4.If both sides stand alone, a comma by itself is a splice, and so is no mark at all. Choose a full stop, a semicolon, or a comma with a joining word such as and, but, so or yet.
  5. 5.If one side cannot stand alone, there are not two sentences to join. A comma follows an opening clause, and a second verb for the same subject takes no mark.

Try it on a question

Work it below before you open the working. The steps say what to do, and you can do each one yourself.

The ropewalk at Sallow Quay was a long, narrow shed. Its spinners walked backwards down the length of it, paying out hemp from a bundle at their ______ finished rope was coiled in a loft at the far end. Nothing else in the village needed so much floor.

Which choice completes the text so that it conforms to the conventions of Standard English?

  1. Choice A: waists, the
  2. Choice B: waists; the
  3. Choice C: waists the
  4. Choice D: waists: the
  1. 1

    Choose a sentence and cover the right side, then the left. Name each side: can it stand alone, or not?

  2. 2

    Try the marks in the slot: no mark, a comma, a comma with a joining word, a semicolon, a colon, a dash and a full stop. The lab says which hold and why.

  3. 3

    Notice that when both sides stand alone, a comma on its own never holds. Then open the sentence that begins with Although: one side cannot stand alone, and a comma is all it needs.

Two sentences, one slot

Sentence 1 of 5

Cover each side in turn. If both can stand alone, a comma on its own will not hold them.

The tide gauge was installed in 1921 the slot its readings were not published for thirty years.

1. Cover one side, then the other. Can each stand alone as a sentence?

Left of the slot

“The tide gauge was installed in 1921”

Right of the slot

“its readings were not published for thirty years.”

2. Try the marks. Which are legal here?

Answer for both sides first.

The full working, and why each wrong choice is there

Cover everything after the gap: "Its spinners walked backwards down the length of it, paying out hemp from a bundle at their waists" stands alone. Cover everything before it: "the finished rope was coiled in a loft at the far end" stands alone too. Two sentences need a full stop, a semicolon, or a comma with a joining word, so the semicolon is the answer. The comma alone is a splice, and the colon would promise an explanation the second half does not give.

  • Choice A: waists, the

    A comma is the lightest way to mark the pause, and the second half follows closely from the first. But each half stands alone, and a comma on its own cannot hold two sentences together.

  • Choice B: waists; thethe answer

    Each half stands alone as a sentence, which is what a semicolon needs. The second half is the next step in the process, not an explanation of the first.

  • Choice C: waists the

    Nothing separates the halves, so the reader runs from the end of one sentence straight into the start of the next. Two sentences need a mark between them.

  • Choice D: waists: the

    A colon promises an explanation or a list. The second half is the next step in the process, so it delivers nothing the colon promised.

Use it when

  • The choices differ in a mark: a comma, a semicolon, a full stop, a colon, or nothing between the same two words.
  • A comma sits between two groups of words that each have a subject and a verb.
  • One choice adds a joining word such as and, but or so, and the others do not.

Do not use it when

  • The choices differ in a verb or a pronoun, not in a mark. Check the subject and the tense instead.
  • A word such as however or therefore sits at the gap. It joins nothing, so the strong mark goes on one side of it and a comma on the other. That takes its own test.
  • The gap is between items in a list, or at the end of an insertion. Those marks come in pairs and series, and whether each side stands alone does not decide them.

Five questions on this move

Untimed, and nothing is saved. A wrong first answer gets one more try before the working is shown.

Question 1 of 5

The orchard at Pell Farm flowers in April, and the keepers bring their hives in from the valley to meet it. Most of the hives stand in rows at the bottom of the ______ few colonies have always nested in the old stone wall above the gate. Nobody has ever tried to move them.

Which choice completes the text so that it conforms to the conventions of Standard English?

Five is a start

In your account there is a focused set of ten on Boundaries from the question bank, with the same one more try. And after each practice test, the drills your plan sets for the skills you missed name the moves for them.

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How this page was checked

  • Every punctuation answer, by our rule table

    For each of the 6 questions on this page, what stands on each side of the blank is recorded, and an automated test checks that our table of punctuation rules calls the keyed choice legal and the other three not.

  • The whole page, by a person

    Not yet. Every question and every item of its lab was worked through in a browser by Claude, an AI assistant, on 14 October 2026. The page was published on 14 October 2026 before a person had read it. If something here is wrong, tell us and it is put right.

The questions were drafted with AI and are original: none is a College Board question, and none comes from the question bank behind our practice tests.

Where this comes from

“Cover each side” is one card from the Preptics lesson Boundaries: what can legally join two sentences, which sits under the Digital SAT skill Boundaries. The lesson has the other cards around it, and its questions come back for review on a schedule. The lessons are part of the Digital SAT track.

Common questions

How do I spot a comma splice on the SAT?
Cover one side of the comma and read the other. Then swap. If each side can stand alone as a sentence, a comma by itself is a splice. The fix is a full stop, a semicolon, or a comma with a joining word such as and, but, so or yet.
Can a comma ever join two sentences?
Yes, when a joining word comes straight after it: and, but, so, yet, or, nor. The comma goes in front of the joining word, never behind it. A comma on its own, or a comma with a word like however, does not join anything.
Is a semicolon or a full stop better between two sentences?
Either does the job, so a question will not make you choose between them unless a capital letter settles it. A semicolon followed by a capital is wrong, and a full stop followed by a small letter is wrong.
A sentence starts with although and has a comma in the middle. Is that a splice?
No. A clause that begins with although or because cannot stand alone, so there are not two sentences to join. Cover the right side and the left side will not make sense by itself. A comma is all the sentence needs.
Does a word like however fix a comma splice?
No. However, therefore and instead can move about inside a sentence, so they join nothing. A comma followed by however is still a splice. The strong mark goes on the far side of the word from the sentence it belongs to, and that needs its own test.

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