A comma splice is when a comma is used unnecessarily. Commas should not be used to split a subject and verb, a compound subject, or a compound verb. Commas are also unnecessary when joining two independent classes or splitting an independent clause from a dependent clause that follows.
If you've ever gotten a paper back and you've seen the letters CS written on it or have all your commas circled and not quite sure why, chances are you probably had some comma splices. So we are going to talk about those comma splices and hopefully help you so that you don't see those marks anymore. So what a comma splice is, is it's essentially just when a comma is used unnecessarily, called the comma splice. Take a look at this example, "The other day I went to the store, to get ingredients for guacamole, I got tomatoes, cilantro and avocados, then I remembered garlic. That's a long sentence but we've got a lot commas in there. We've got one here, we've got one here and we've got one here. So let's take a look at those. "The other day I went to the store, to get ingredients." Now going to the store to get ingredients is all part of the same verb phrase. So we don't want this comma here, we do not want to split up that verb phrase. And if we come here, "I got tomatoes, cilantro and avocados." So those are commas in a list, this one's okay but if we look here then, "comma then I remembered garlic." here we've got two independent clauses, "I got tomatoes, cilantro and avocados," and then "then I remembered garlic" joined together with just a comma and we know that that's not one of the comma rules so we've got another comma splice here. So let's talk about some different ways to identify those unnecessary commas. So, basic tricks are; don't use a comma to split a subject and a verb up, don't use a comma to split a compound subject, don't use a comma to split a compound verb. And then here's the big one; don't use a comma to join two independent clauses if that's all you're using. The simple fix to that is just to throw a FANBOY in there. So we could say, "I got tomatoes, cilantro and avocados and then I remembered garlic." and you've got a grammatically correct sentence. But if you're just using a comma to join those two independent clauses, you've got to add something else there. And finally, don't use a comma to split an independent clause from a dependent clause when the dependent clause follows, so you don't need any mark there. Let's take a look at some examples. Alright, this first one. "I grow cilantro in my garden, because it is one of my favorite herbs." So we've got a comma here and that's actually a comma splice. If you look we've got this first part of the sentence is an independent clause, it can stand on it's own, it's got a subject and a verb and afterwards we've got a dependent clause. So we've got a subject and a verb but it doesn't express a complete thought because it starts with one of those subordinating conjunctions. And we learned, if your using a comma to join an independent to a following dependent, it's a comma splice, you don't need a comma there. Alright, let's look at this one and see if you can find out what's wrong with it. "Once you get the cilantro plants growing, they are difficult to kill, and get rid of." Alright, so we've got two commas there. Let's look at the first one, "Once you get the cilantro plants growing," you've got a dependent clause then you've got comma and it says, "they are difficult to kill and get rid of." you've got an independent clause here hooked by a comma, so that comma's okay to stay there. But if we move down to this comma here, we've got, "they are difficult to kill and get rid of" and one of our rules for avoiding comma splices is don't use a comma to split up a compound verb; here our subjective they, and what are they doing? They are being difficult to kill and get rid of and we don't want this comma splitting that verb up, so make sure that you eliminate that. Finally, "Did you know that Coriander seeds, are the seeds of the cilantro plants?" We've got a comma here. If we take a look at what it's splitting over on this side, we've got coriander seeds which is an object, kind of the subject of what we're talking about. And here, we've got the verb that connects to those coriander seeds and we said, one of our tricks was; don't use a comma to split up the subject and the verb. So we have another comma splice here. Alright, let's step over here and see if you can find the comma splices in this sentence. So, we've got, "Fats found in avocados, olive oil, nuts and fatty fish help lower overall, and bad cholesterol. They can also, help with memory." Alright, so let's go through our commas; we've got one, two, three, four, five commas. And if we look at this first sentence, we've got a list of items, so our commas should be here, we're good here, here and here. They are just separating items in a list. But when we get to this comma, "help lower overall, and bad cholesterol." Alright, we've got overall and bad both describing cholesterol but we've got this word "and" here, "and" and the comma are redundant, so we can lose the comma, in that case it's a comma splice, alright. And then in the last sentence, "they can also help, with memory." Again, we see a subject over here, part of a verb phrase here and then the other part here with the comma in between. So we want to make sure we get rid of that so our whole verb phrase can stay together. So you've taken a look at some of the most common errors with common splices. Just remember these simple tricks, don't use the comma to split a variety of things, you should be good to go.