First, you need to distinguish between a dependent and an independent clause.
Coordinate sentences consist of two or more independent clauses. Use a coordinate sentence to create a balanced sentence with equal emphasis on each clause and to show relationships between ideas.
In the first pattern, below, the independent clauses are joined by a comma and a coordinating conjunction. (The seven coordinating conjunctions in English are listed in the brackets). The first letters of the coordinating conjunctions spell “fanboys,” a way to remember them. In the second pattern, they are joined by a semi-colon (;) and a word that clarifies their relationship; this word is called a conjunctive adverb, and the list here is representative but not exhaustive. In the third pattern, they are simply joined by a semi-colon.
Ex. 1 Reveille gets royal treatment, but she works hard to foster school spirit.
Ex. 2 Reveille gets royal treatment; however, she works hard to foster school spirit.
Ex. 3 Reveille gets royal treatment; she works hard to foster school spirit.
Subordinate sentences consist of a dependent clause and an independent clause. Use a subordinate sentence to emphasize the independent clause and to show relationships between ideas. Dependent clauses begin with a subordinating conjunction, examples of which are shown in the brackets.
The dependent clause and the independent clause can be reversed in order. In pattern 1, the Independent clause comes first, so there is no comma between the clauses. In pattern 2, the independent clause comes last, so there is a comma between them.
Ex. 1. Reveille gets royal treatment because she works hard to foster school spirit.
Ex. 2. Because Reveille works hard to foster school spirit, she gets royal treatment.