Comma Splices: What They Are and How to Fix Them

The comma splice is the punctuation error professors flag most, and it hides in otherwise strong writing. The good news: once you can spot it, there are four clean ways to fix it, and you get to pick the one that reads best.

What a comma splice is

A comma splice happens when you join two complete sentences with only a comma. Each half could stand on its own, so a comma alone is too weak to hold them together.

The four fixes

Any of these fixes it; choose by how the sentences relate and how you want it to read.

• Use a period, if the two ideas are separate: The experiment failed. We ran it again.
• Use a semicolon, if they are closely linked: The experiment failed; we ran it again.
• Add a coordinating conjunction after the comma (and, but, so, for, or, nor, yet): The experiment failed, so we ran it again.
• Make one half depend on the other with a word like because or although: Because the experiment failed, we ran it again.

How to catch your own

When you hit a comma, check whether both sides could stand alone as full sentences. If they can, and there is no 'and', 'but', or 'so' after the comma, you have a splice, and one of the four fixes will clear it.