Fixing Comma Splices

Written by Jerry Plotnick, University College Writing Centre

What is a Comma Splice?

A comma splice occurs when you use a comma to join two complete sentences without placing an appropriate joining word between them. The comma just isn’t strong enough to do the job of making one grammatical sentence out of two. Learn to recognize what comma splices look like, and be sure to avoid them in your essays.

Here is a simple example of a comma splice:

  • I completed my essay, I have not submitted it.

A closely related grammatical error is the run-on sentence. It occurs when you join two complete sentences without any punctuation mark at all:

  • I completed my essay I have not submitted it.

Fixing a run-on sentence is no different from fixing a comma splice.

Some Basic Definitions

The grammatical term for a group of words that can stand on its own as a complete sentence is independent clause. To be an independent clause, the group of words must contain both a subject and a verb. In the independent clause I completed my essay, I is the subject, and completed is the verb.

The grammatical term for a joining word is conjunction. Conjunctions refer to those words in the English language such as and or but or since or because that allow us to build more complex sentences out of simpler ones. The conjunctions and and but are called coordinating conjunctions; the conjunctions since and because are called subordinating conjunctions.

It is not essential to remember these grammatical terms, though they can be useful for conveying important points about grammar. What really matters is to know comma splices when you see them and to be familiar with the various ways of fixing them.

How to Fix a Comma Splice

Here are four straightforward ways to solve the comma splice problem. Understand the subtle differences between them, and make sure you don’t get into the habit of always solving your comma splice problems in the same way. Look at each comma splice in your writing as an opportunity to gain mastery over the tools for building complex sentences out of simpler ones.

Solution 1: Use a period.

The simplest way to fix a comma splice is to separate the two improperly joined sentences. Simply replace the comma with a period. The two sentences may sound a bit abrupt placed one after the other, but at least they will be grammatical:

  • I completed my essay. I have not submitted it.

A period may be your best choice for fixing a comma splice when any of the following conditions holds: (1) the logical connection between the two independent clauses is self-evident; (2) one or both of the clauses is long; or (3) the ideas represented in the two clauses are distinct.

  • I completed my English essay. Now I must go to the library and begin research at once on my fifteen-page History term paper.

Solution 2: Use a semi-colon.

If you want a simple solution to the comma splice, but you prefer to encapsulate your two ideas in one sentence rather than two, then use a semi-colon rather than a period:

  • I completed my essay; I have not submitted it.

A semi-colon is probably the most appropriate remedy for your comma splice when the following two conditions hold: (1) the logical connection between the two independent clauses is already clear, and (2) the ideas represented in the two clauses are very closely related. In particular, when the relation between the two clauses is one of sequence-either a sequence in time or a logical sequence-then a semi-colon is just what you need:

  • I completed my English essay; next I will tackle my History essay.

Solution 3: Use a coordinating conjunction.

Like the semi-colon, a conjunction allows you to combine your two ideas in a single sentence. But it has the added advantage of allowing you to indicate the logical relationship between the two ideas. In our comma splice example, the relationship is one of contrast: I completed the essay, but I haven’t submitted it even though that would have been the expected thing to do.

The coordinating conjunction but compactly conveys this sense of the unexpected or contradictory:

  • I completed my essay, but I have not submitted it.

In all, there are seven coordinating conjunctions:

and, but, or, nor, for, so, yet

They cover the most basic kinds of logical relationships that can exist between two separate ideas.

Solution 4: Use a subordinating conjunction.

Subordinating conjunctions are similar to coordinating conjunctions in that they allow you to indicate the logical relationship between two independent clauses. However, unlike coordinating conjunctions, subordinating conjunctions lay unequal stress on the two parts of the new sentence. We can use the subordinating conjunction although to solve our comma splice problem, and we can do so in two distinct ways

  • I completed my essay, although I have not submitted it.
  • Although I completed my essay, I have not submitted it.

As the word subordinating suggests, we place less stress on the clause introduced by the subordinating conjunction. In the first example, the fact that I have not submitted the essay appears as an afterthought; in the second example, it is the point.

There are a great many subordinating conjunctions in the English language. Here are a few of the more common ones:

while, although, because, if, since, unless, whether, when, why, as, before, after, if, whether, that, once

How Not to Fix a Comma Splice

Never try to join two sentences with a comma followed by a conjunctive adverb. The most common form this error takes involves joining two sentences with the word however:

  • I completed my essay, however I have not submitted it.

This sentence is still a comma splice. Learn to distinguish conjunctive adverbs from subordinating conjunctions; they do not function in the same way. Conjunctive adverbs should be used to begin independent clauses, not to join them.

Here is just a small sample of the many conjunctive adverbs that are available to you. Notice that conjunctive adverbs can consist of phrases as well as single words:

however, nevertheless, furthermore, moreover, hence, therefore, similarly, certainly, by contrast, in other words, in addition

Note that you can use a conjunctive adverb to help fix a comma splice, but you must remember to put a period or a semi-colon in front of the second independent clause:

  • I completed my essay. However, I have not submitted it.
  • I completed my essay; however, I have not submitted it.

A conjunctive adverb like however usually makes for a more formal and more emphatic transition between clauses than the more casual conjunctions but and although. If you rely too heavily on conjunctive adverbs, your writing will begin to sound stiff. Save your howevers for when you really need them: (1) for emphasizing the key turns in your argument, or (2) for signaling a contrast between long, complex sentences. Many stylists prefer not to use however right at the beginning of a sentence.

  • I completed my essay in just one draft, a process that took me only three hours. This last essay, however, was a mere two pages long, and I have learned the hard way that neglecting to revise my papers inevitably results in a weaker paper and a lower grade.