What is a comma splice on the ACT?

A comma splice is what you get when two complete sentences are glued together with nothing but a comma. A comma is not strong enough to hold two independent clauses on its own, and the ACT knows that most students read right past the mistake. Once you can spot a splice in about three seconds, a whole family of English questions gets easier, because the fixes are always the same four moves.

What makes a splice a splice

An independent clause has a subject and a verb and could stand alone as a sentence. Put two of them next to each other with only a comma between, and you have a splice: The rehearsal ran long, we ordered pizza afterward. Both halves could be their own sentence, so the comma is doing work it isn't allowed to do. Compare that with Because the rehearsal ran long, we ordered pizza afterward. Now the first half depends on the second, and the comma is perfectly happy. That's why getting comfortable with independent and dependent clauses pays off across the entire section.

The four ways to fix one

• Use a period. The rehearsal ran long. We ordered pizza afterward.
• Use a semicolon. The rehearsal ran long; we ordered pizza afterward.
• Add a coordinating conjunction after the comma. The rehearsal ran long, so we ordered pizza afterward. Your options are for, and, nor, but, or, yet, and so.
• Make one clause dependent. Since the rehearsal ran long, we ordered pizza afterward.

All four are grammatically correct, which means the ACT will pick the one that fits the tone and flow of the passage. Your job is usually just to eliminate the choices that leave the splice in place.

Correct versus incorrect, side by side

• Splice: Ana finished the lab report, Devon checked the math. Fixed: Ana finished the lab report, and Devon checked the math.
• Splice: The trail was steep, we stopped twice to catch our breath. Fixed: The trail was steep, so we stopped twice to catch our breath.
• Splice: He had never seen the ocean, it was bigger than he expected. Fixed: He had never seen the ocean; it was bigger than he expected.
• Not a splice: Walking home in the rain, she thought about the conversation. The opening phrase has no subject and verb of its own, so a comma is exactly right.

The traps to watch for

The classic setup is a question where all four answer choices contain the same words and differ only in punctuation. That's a signal that meaning won't help you, so go straight to structure and count the complete sentences.

Watch out for words like however, therefore, moreover, and instead. These feel like conjunctions, but they are not, so they can't patch a splice. The forecast called for snow, however the roads stayed clear. is still a splice. You need The forecast called for snow; however, the roads stayed clear. There's more on that pattern in how semicolons work on ACT English.

One more useful shortcut: a semicolon and a period do the same job here. If two answer choices are identical except that one uses a period and the other uses a semicolon, neither can be correct, because a question can't have two right answers. That elimination alone can save you thirty seconds.

A self-check that takes three seconds

Cover the comma with your finger and read each side on its own. If both sides sound like finished sentences, you've found a splice and the comma has to change. If one side is missing a subject or a verb, or if it starts with a word like because, although, or while, the comma is probably fine. Run that check on ten sentences in a row and it stops feeling like a rule and starts feeling like a reflex.

How to practice this

Grab any paragraph you wrote for English class and hunt for splices in your own writing first. It's surprisingly effective, because you already know what you meant, so the structure is all that's left to look at. From there, do focused sets rather than scattered practice. thirty-six has concept quizzes that stack these questions together so you can build the reflex quickly. When splices feel routine, move on to run-on sentences and then zoom out to the broader grammar rules the ACT tests. Since there's no penalty for guessing, always put down an answer even when two choices look equally good.

This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.