Compound and Complex sentences 
A compound sentence is two simple sentences joined by a comma and a conjunction such as and, but, etc.
A compound sentence expresses two complete thoughts.
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Nare and Vardan waited for the train, but the train was late.
Nare and Vardan arrived at the station early, and they left before I arrived.
A complex sentence is made up of a main/independent clause and one or more dependent clauses.
An independent clause is a complete thought. It can stand alone as a sentence.
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I am hungry.
A dependent clause is not a complete thought. It cannot stand alone as a sentence.
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When I get up in the morning
The dependent clause usually begins with a subordinating conjunction such as because, as, after, before, while, until, since, unless, although, if, etc.
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Because Nare and Vardan arrived at the station early, I did not see them at the station.
I need to return this book before the library closes.
Unless it's cloudy tonight, we will see the full moon.
I was late this morning because I forgot to set my alarm.