Comma Splices and Fused Sentences

To combine two complete sentences (“independent clauses“) correctly, you can do the following things: use a comma and a coordinating conjunction (“for, and, nor, but, or, yet, so”); use a semi-colon (and/or a semi-colon with a conjunctive adverb, like “nevertheless”); make one clause dependent on the other (by adding a “dependent marker word” like “because”); or use a period and begin a new sentence.

Here is an example to illustrate the rule: take the sentences, “I like watching movies” and “My roommate likes listening to music.” These are both very short sentences, so you may want to combine them to form a longer sentence. However, if you want to combine them, you have to be careful not to create a fused sentence or a comma splice.

The wrong ways:

If you put the sentences together with no punctuation at all — “I like watching movies my roommate likes listening to music” — you create a fused sentence.

If you join them with nothing but a comma — “I like watching movies, my roommate likes listening to music” — you create a comma splice.

If you join them with a conjunctive adverb (e.g., “however”) — “I like watching movies, also, my roommate likes listening to music” or “I like watching movies however my roommate likes listening to music” — you create a fused sentence or comma splice (depending on whether you’ve also used a comma).

Fused sentences (“run-ons”) and comma splices are X errors that will make your essays ineligible for use in your portfolio.

The right ways:

You can combine sentences with a semi-colon: “I like watching movies; my roommate likes listening to music.”

You can also add a conjunctive adverb after a semi-colon to correctly separate sentences: “I like watching movies; moreover, my roommate likes listening to music.”

You can also combine sentences by using a comma and a coordinating conjunction (“for, and, nor, but, or, yet, so”): “I like watching movies, but my roommate likes listening to music.”

You can make one sentence dependent on the other by adding a dependent marker word: “I like watching movies while my roommate likes listening to music” or “While I like watching movies, my roommate likes listening to music.”

Finally, while you should avoid using a lot of short, choppy sentences in your writing, it is better to have a problem with your writing style than your grammar. There is nothing grammatically wrong with keeping these two sentences separate: “I like watching movies. My roommate likes listening to music.” Remember the golden rule of writing — “avoid trouble” — and write sentences you know are correct and complete even if you fear they “sound bad.”

Note that sometimes writers who are proficient in grammar choose to use comma splices for stylistic reasons (e.g., “Ian Curtis doesn’t try to dance, dance tries to Ian Curtis”), but my advice is to save the “literate comma splices” for your first novel.

Sentence Fragments

All complete sentences have two things: a main “subject” (the thing or person that acts) and a “predicate” (a word or group of words containing the main verb — the verb that shows the subject’s action). Even very short sentences like “I studied” or “He danced” are complete because they have these two necessary grammatical “parts.” Grammatically incomplete groups of words punctuated like sentences are called “sentence fragments,” and sentence fragments are considered “serious” grammatical errors because they show that a writer does not have full control over his or her ideas.

I see two main kinds of sentence fragments in student writing:

1) Some sentence fragments result when a group of words is set off as a complete sentence, but that group lacks a subject or a main verb (or both). Many times, this kind of sentence fragment is actually just a group of words that belongs at the end of the previous sentence, as in the following example from a student paper: “Jove appears to be a lustful god because he rapes many nymphs. For instance, Callisto and Io.” The group of words after the period completes the sentence that comes before it, so the fragment should be joined to that sentence with a comma.


“I have traveled out of the country a few times. Once to England, once to Spain, and once to Canada.”

“Some early important mathematicians and computer programmers were women. For example, Hypatia and Ada Lovelace.”

2) Sentence fragments can also result when a complete sentence (an “independent clause”) is preceded by something called a “dependent marker word” – a word that makes all the words in the ensuing clause a fragment of an idea, “dependent” on other, independent clauses.

Back to our first example, then: “He danced” can stand alone as a complete sentence, but not if we put a dependent marker word like “when” or “while” in front of it. “When he danced” is a “dependent clause” — it begins with a dependent marker word — but you can also probably hear that the clause is not “complete”: it does not give readers the information we need to understand the writer’s point. In fact, the clause leaves us wondering, “what happened when he danced?” If we join this dependent clause with an independent clause, it can act as part of a complete sentence that gives all the information we want to convey. For example, we could put the clause at the beginning of a complete sentence and write, “When he danced, everyone stopped and stared,” or we could start the sentence with an independent clause and put our dependent clause at the end: “The room fell silent when he danced.”

Remember that length has nothing to do with whether a sentence is grammatically complete. Even long groups of words beginning with dependent marker words cannot stand alone and need to be joined to complete sentences, as in the following.


In the story of Phaethon, a character who needs to prove that he is his father’s son falls to his death. While in the story of Icarus a boy who doesn’t listen to his father flies too high and faces the consequences.

The second group of words, long though it is, is not a complete thought; it makes us wonder, “while what? This stuff is true of Icarus, while … ?” In this example, then, a comma needs to join the independent and dependent clauses to make the latter part of a complete sentence.

One way to begin to avoid or correct sentence fragments is to memorize and look for dependent marker words (go on a “which hunt”). The most common dependent marker words include “after,” “although,” “as,” “as if,” “because,” “before,” “even if,” “even though,” “if,” “in order to,” “since,” “though,” “unless,” “until,” “whatever,” “when,” “whenever,” “whether,” “which,” and “while.” When you start a sentence with one of these words, you need to ensure that you have joined the dependent clause it introduces to an independent clause preceding or following the fragment.

Subject-Verb Agreement Errors

The last type of “X error” we’ll discuss here is called the “subject-verb agreement error.” This type of error results when we match subjects and verbs that do not agree in number.

Most native speakers of English can “hear” whether subjects and verbs agree or not. For instance, you probably know that “The soldiers march in line,” not “The soldiers marches in line,” and that “The dancers are very talented,” not “The dancers is very talented.”

However, even native English speakers can accidentally mismatch subjects and verbs in their writing. The error tends to occur in the following situations:

1. When we use certain contractions. “Doesn’t” is a contraction of “does not” and should be used only with a singular subject. “Don’t” is a contraction of “do not” and should be used only with a plural subject. “There’s” is a contraction of “there is” and should be used only with a singular subject.

Incorrect: There’s two mistakes in this sentence.
Incorrect: Narcissus don’t recognize his reflection.

Correct: There are two mistakes in this sentence.
Correct: Narcissus doesn’t recognize his reflection.

2. When we begin sentences with “there is” or “there are”: as in the first example above and the example below, the subject follows the verb in this type of sentence. “There” is not the subject, so the verb must agree with whatever follows.

Incorrect: There is many similar stories.
Correct: There are many similar stories.

3. When we use the words “each,” “each one,” “either,” “neither,” “everyone,” “everybody,” “anybody,” “anyone,” “nobody,” “somebody,” “someone,” and “no one” as subjects: these words are all singular and require singular verbs.

Incorrect: Each of the gods are emotional.
Incorrect: Either of the girls’ opinions are valid.

Correct: Each of the gods is emotional.
Correct: Either of the girls’ opinions is valid.

4. When phrases separate the subject and the verb in a sentence. The main verb must agree with the sentence’s subject, not with any given noun or pronoun in the intervening or subordinate clause or phrase.

Incorrect: One of the gods are vengeful.
Incorrect: The people whom Juno punishes is many.

Correct: One of the gods is vengeful.
Correct: The people whom Juno punishes are many.