A clause is a group of words that includes two obligatory elements:
- a subject – expresses who or what does something. To find the subject, ask who or what performs the activity.
- a predicate – the word expressing the activity. The predicate changes its form depending on the subject (I play but he plays) and depending on the tense (he plays often but he played yesterday). The predicate is always a verb; hence, the easiest way to find the predicate of the clause is to find the verb whose form changes depending on the subject and the tense.
(1) Mary is writing a letter. [Mary is the subject, writes is the predicate]
(2) The new theory captures the data successfully. [the new theory is the subject, captures is the predicate]
There are two types of clauses:
- independent clause – it expresses a complete thought and can stand alone.
(3) John was hired by an IT company.
(4) The majority of politicians do not accept global warming as a real threat.
- dependent clause – it does not express a complete thought but just a part of it. Dependent clauses cannot stand alone.
(5) shortly after he graduated in Computer Science [an incomplete thought]
(6) although scientists have found strong indications of a global temperature rise [an incomplete thought]
Dependent clauses are commonly introduced by special markers (called subordinate conjunctions), such as, if, whether, because, although, since, when, while, unless, even though, whenever (follow this link for a fuller list).
A sentence consists of one or more clauses. A sentence that is made up of a single clause is a simple sentence. The single clause has to be an independent clause in order for the sentence to be complete. The examples in (1)-(4) are all simple sentences consisting of just one independent clause.
A sentence can also contain more than one clause. Such a sentence is called a compound sentence. Compound sentences can consist of two or more independent clauses (connected by and, but, or, nor)
(7) John was hired by an IT company, but Mary did not find a job.
(8) We have to finish the project first, and then we can take a holiday.
A compound sentence can also combine independent clauses with dependent clauses.
(9) Shortly after John graduated in Computer Science, he was hired by an IT company.
(10) The majority of politicians do not accept global warming as a real threat, although scientists have found strong indications of a global temperature rise.
A compound sentence has to contain at least one independent clause to be complete.
Sometimes, complex phrases can be used instead of a dependent clause to encode the same information. This creates a longer simple sentence with just one subject and one verb.
(11) Shortly after his graduation in Computer Science, John was hired by an IT company.
(12) The majority of politicians do not accept global warming as a real threat despite the strong indications of a global temperature rise.
The groups of words “shortly after his graduation in Computer Science” and “despite the strong indications of a global temperature rise” are not clauses because they have no subject (the words John and scientists are missing) and no predicate (graduation is not a verb but a noun derived from a verb).
Summary:
This handout defines dependent and independent clauses and explores how they are treated in standard usage.
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.
Independent Clause
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.
Dependent Clause
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 that makes it into a dependent clause.
When Jim studied in the Sweet Shop for his chemistry quiz, it was very noisy.
Some common dependent markers: after, although, as, as if, because, before, even if, even though, if, in order to, since, though, unless, until, whatever, when, whenever, whether, and while.
Connecting independent clauses
There are two types of words that can be used as connectors at the beginning of an independent clause: coordinating conjunctions and independent marker words.
1. Coordinating Conjunction
The seven coordinating conjunctions used as connecting words at the beginning of an independent clause are and, but, for, or, nor, so, and yet. 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.
2. 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: also, consequently, furthermore, however, moreover, nevertheless, and therefore.
Connecting dependent and independent clauses
Subordinating conjunctions allow writers to construct complex sentences, which have an independent clause and a subordinate (or dependent) clause. Either clause can come first.
The students acted differently whenever a substitute taught the class.
Whenever a substitute taught the class, the students acted differently.
Note that the clauses are separated with a comma when the dependent clause comes first.
Some common subordinating conjunctions: after, as, before, once, since, until, and while.
Some Common Errors to Avoid
Comma Splices
A comma splice is the use of a comma between two independent clauses. You can usually fix the error by changing the comma to a period and therefore making the two clauses into two separate sentences, by changing the comma to a semicolon, or by making one clause dependent by inserting a dependent marker word in front of it.
Incorrect: I like this class, it is very interesting.
- Correct: I like this class. It is very interesting.
- (or) I like this class; it is very interesting.
- (or) I like this class, and it is very interesting.
- (or) I like this class because it is very interesting.
- (or) Because it is very interesting, I like this class.
Fused 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.
Incorrect: My professor is intelligent I've learned a lot from her.
- Correct: My professor is intelligent. I've learned a lot from her.
- (or) My professor is intelligent; I've learned a lot from her.
- (or) My professor is intelligent, and I've learned a lot from her.
- (or) My professor is intelligent; moreover, I've learned a lot from her.
Sentence Fragments
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.
Incorrect: Because I forgot the exam was today.
- Correct: Because I forgot the exam was today, I didn't study.
- (or) I forgot the exam was today.