How to fix one of the most common writing errors.
How to Use a Semicolon to Fix a Comma Splice
If the two sentences are closely related to each other, as they are in the sentence from Ancestor, you can use a semicolon to connect them without a coordinating conjunction.
Sara obviously named that one; she was a sucker for those old “Happy Days” reruns.
The semicolon makes sense because the second clause expands on the reasoning of the first clause. He's saying that it's obvious that Sara named the cow because she liked “Happy Days” reruns and the cow is named after a “Happy Days” character. (Want more? See Episode 189, How to Use Semicolons.)
You can think of a semicolon as a “sentence splicer” because its job is to splice complete sentences together.
How to Use Coordinating Conjunctions to Fix a Comma Splice
Sometimes, you can also fix a comma splice by adding a coordinating conjunction. It doesn't work with the example sentence from Ancestor because it doesn't make any sense to add an “and” or any of the other coordinating conjunctions. It changes the meaning to say Sara obviously named that one, and she was a sucker for those old “Happy Days” reruns.
But if I go back to the other sentence with a comma splice—Squiggly ran to the forest, Aardvark chased the peeves—you can see that it makes sense to connect those two sentences with a coordinating conjunction and a comma.
Squiggly ran to the forest, and Aardvark chased the peeves.