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Complex Sentence and Clauses

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A complex sentence includes one complete sentence (called as main clause or independent clause) and one or more dependent clauses. A complex sentence is different than a compound sentence (see Conjunctions).

A compound sentence contains two or more complete sentences separated by punctuation.


I believe hard work deserves recognition, therefore I reward hard work of my employees with praise, promotion and salary increase.

This sentence has two complete sentences and linked with the conjunction 'therefore'.

Complex sentence:

A complex sentence includes at least two complete sentences: an independent clause (or main clause) and a dependent clause. A clause begins with words such as 'who, what, which, when, that'. These words, called as clause markers, replace the subject, object or adverb in a complex sentence. An example:

Mark Twain, who is a famous American novelist, illustrated American life in the industrialization period in his novels.

The Dependent Clause "who is a famous American novelist" begins with the clause marker (who) but it can't stand alone by itself. This dependent clause replaces the subject "Mark Twain".

The Independent Clause, "Mark Twain illustrated American life in the industrialization period in his novels." stands alone to carry a complete thought in this complex sentence, without the inclusion of the dependent clause, "who is a famous American novelist".

This complex sentence has one independent clause and one dependent clause. Notice the commas separating the dependent clause from the independent clause--the non-essential part of the sentence. The clause marker, "who", forms a noun clause with a subject and a verb and operates as a noun and cannot stand alone as a sentence. The independent clause "Mark Twain illustrated American life in the industrialization period in his novels." is one complete sentence because it contains a subject, verb, and expresses a complete thought without the help of the dependent clause.

In a complex sentence, clauses give more information about the subject, object or adverb so we define them as to which part of the sentence they describe further. The types of clauses used in English are: noun clause, adjective clause and adverb clause.

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Noun Clause
: As you see above in the example, a noun clause describes a noun in the sentence that could be the subject or the object of the sentence. In the example above, the noun clause describes the subject Mark Twain.

The teacher, who had a British accent, confused the student.

In this sentence, the noun clause is a dependent clause; it has a subject and verb and helps to further describe the subject but doesn't express a complete thought by itself. The noun clause is separated with commas from the main clause (The teacher confused the student.)

See more noun clauses.

Adjective Clause has a subject and a verb, and takes the place of an adjective. An adjective clause must be connected to an independent clause.


"Faraday first worked as a bottle washer for the famous chemist Humphry Davy, who later had become very jealous of him."

Adjective clause: "who later had become very jealous of him."

Main clause: "Faraday worked as a bottle washer for the famous chemist. The main clause can stand by itself because it expresses a complete thought."

"Faraday discovered that electricity moves through wire." In this sentence, conductivity of wire is not mentioned, but it is described as the 'object' of the sentence. This sentence has two independent clauses:

The first independent clause:" Faraday discovered that". In this sentence 'that" is a clause marker acting as the object of the sentence.

The second independent clause, "the electricity moves through wire", replaces the object "that" and carries a complete thought.

The above two clauses are independent because they both have a subject and verb, and impart a complete thought thus an stand alone.

Hint: You can recognize an adjective clause because it always contains a subject, verb and a clause marker. Study the examples below.

Examples for Adjective Clauses:

Adjective Clauses
Clause Marker
Used with, for
who people (subject) The Amish who live in Lancaster, Pennsylvania practice simplicity by abstaining from technology.
whom people (object) The woman whom I met in London was an aristocrat.



The woman whose children had been killed in the car accident cried very hard.



Those are colors which I wear all the time.
that people/things
The Chinese are the people that I want to learn about.
where place That is the city where my parents live.
when time I travel when I have money.

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An Adverb clause is a dependent clause that takes the place of an adverb. An adverb clause answers questions such as when, where, why, with what result, under what conditions, and for what purpose.

I watched a movie last night. 'Last night' is an adverb.

I watched a movie after I came home. 'After I came home' is the adverb clause in this sentence. It takes the place of the adverb. As you see, the adverb clause is dependent of the main clause "I watched a movie", which is a complete sentence. The adverb clause does the same job as the adverb.

Types of Adverb Clauses

Adverb Clauses
Clause Marker
Used with, for
when time (adverb) I studied law when I was in college.
after time/action/things (object) I had studied law after graduating with pre-law degree.

time/action/things (adverb/object)


I had studied pre-law before I went to law school.

reason (adverb)


We know why children learn quickly.
where place (adverb)
I found my keys in the waiting room where I placed a telephone call.
how under what conditions (adverb) I don't understand how I can cook for a dozen people without help this weekend.
how with what result (adverb) My parents never understood how I married a poor man for love only


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