When you want to use commas and semicolons in sentences and when you are concerned about whether a sentence is or is not a fragment, a good way to start is to be able to recognize dependent and independent clauses. The definitions offered here will help you with this.
An independent clause is a group of words that contains a subject and verb and expresses a complete thought. An independent clause is a sentence.
Jim studied in the Sweet Shop for his chemistry quiz.
A dependent clause is a group of words that contains a subject and verb but does not express a complete thought. A dependent clause cannot be a sentence. Often a dependent clause is marked by a dependent marker word.
When Jim studied in the Sweet Shop for his chemistry quiz (What happened when he studied? The thought is incomplete.)
Dependent Marker Word
A dependent marker word is a word added to the beginning of an independent clause; the dependent marker word is what makes the clause into a dependent clause.
When Jim studied in the Sweet Shop for his chemistry quiz, it was very noisy.
Some common dependent markers are:
- as if
- even if
- even though
- in order to
Types of dependent or subordinate clauses
Dependent clauses can function as nouns, adjectives, and adverbs. So, you can have:
- noun clause
- adjective clause
- adverb clause
Note: Adjective clauses are also called relative clauses, and they come in two flavors: restrictive and nonrestrictive.
A noun clause can replace any noun in a sentence, functioning as a subject, object, or complement (see English Grammar: Basic Sentence Elements).
The boy wondered if his parents bought him what he wanted for Christmas.
In this sentence, the noun clause, if his parents bought him what he wanted for Christmas, is the direct object.
Adjective clause (or relative clause)
An adjective clause describes a noun just like an adjective.
I listened to the song that you told me about.
Which song? The new song? The good song? No, the song that you told me about.
Often called relative clauses, adjective clauses are either restrictive or nonrestrictive (also called defining and non-defining, essential and nonessential, or integrated and supplementary):
A restrictive clause begins with a relative pronoun like that or who (or sometimes which – see Which Versus That). It specifies or restricts the noun:
The building that they built in San Francisco sold for a lot of money.
In this case, the restrictive clause specifies which building the speaker is referring to.
Note: the relative pronoun is often omitted (“The building (that) they built”), leaving what is called an elliptical clause or contact clause.
A nonrestrictive clause begins with a relative pronoun like which or who. It adds extra information about an already-specific noun.
The building, which they built in San Francisco, sold for a lot of money.
In this case, there’s only one building to talk about, whereas the example for the restrictive clause implies that there could be several buildings.
Like all adverbials, adverb clauses express when, where, why, and how something occurs.
I’ll do the laundry when I’m out of clothes.
A dependent clause is an adverb clause if you can replace it with an adverb, as in I’ll do the laundry later.
Connecting dependent and independent clauses
There are two types of words that can be used as connectors at the beginning of an independent clause:
- coordinating conjunctions
- independent marker words
The seven coordinating conjunctions used as connecting words at the beginning of an independent clause are:
You can remember them using the acronym: FANBOYS
When the second independent clause in a sentence begins with a coordinating conjunction, a comma is needed before the coordinating conjunction:
Jim studied in the Sweet Shop for his chemistry quiz, but it was hard to concentrate because of the noise.
Independent marker word
An independent marker word is a connecting word used at the beginning of an independent clause. These words can always begin a sentence that can stand alone. When the second independent clause in a sentence has an independent marker word, a semicolon is needed before the independent marker word.
Jim studied in the Sweet Shop for his chemistry quiz; however, it was hard to concentrate because of the noise.
Some common independent markers are:
Some common errors to avoid
A comma splice is the use of a comma between two independent clauses. There are several ways to fix comma splices:
- change the comma to a period and therefore make two clauses into two separate sentences
- change the comma to a semicolon
- make one clause dependent by inserting a dependent marker word in front of it
Here are some examples:
- Comma splice: I like this class, it is very interesting.
- Correct: I like this class. It is very interesting.
- Correct: I like this class; it is very interesting.
- Correct: I like this class, and it is very interesting.
- Correct: I like this class because it is very interesting.
- Correct: Because it is very interesting, I like this class.
Fused or Run-on sentences
Fused sentences happen when there are two independent clauses not separated by any form of punctuation. This error is also known as a run-on sentence. The error can sometimes be corrected by adding a period, semicolon, or colon to separate the two sentences.
- Fused or Run-on sentence: My professor is intelligent I’ve learned a lot from her.
- Correct: My professor is intelligent. I’ve learned a lot from her.
- Correct: My professor is intelligent; I’ve learned a lot from her.
- Correct: My professor is intelligent, and I’ve learned a lot from her.
- Correct: My professor is intelligent; moreover, I’ve learned a lot from her.
Sentence fragments happen by treating a dependent clause or other incomplete thought as a complete sentence. You can usually fix this error by combining it with another sentence to make a complete thought or by removing the dependent marker.
- Sentence fragment: Because I forgot the exam was today.
- Correct: Because I forgot the exam was today, I didn’t study.
- Correct: I forgot the exam was today.